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SCIENCE DOCUMENTS<br />
SECTION<br />
Title Version Reference Date Coordinator Page<br />
Executive<br />
summary and<br />
fast facts 1.0 MUSE-MEM-GEN-056 04/02/2004 R. Bacon 003/007<br />
Science case 1.3 MUSE-MEM-SCI-052 04/02/2004 R. Bacon 008/107<br />
Exposure time<br />
calculator and<br />
per<strong>for</strong>mance<br />
analysis 1.2 MUSE-MEM-SCI-051 15/01/2004 R. Bacon 108/165<br />
Science<br />
preparation and<br />
science team<br />
organisation 1.0 MUSE-MEM-SCI-053 02/02/04 R. Bacon 166/190<br />
Data analysis<br />
software 2.2 MUSE-MEM-SCI-054 29/01/2003 E. Emsellem 190/197
This report summarizes the results of the<br />
Phase A study of the Multi Unit<br />
Spectroscopic Explorer (MUSE), a second<br />
generation VLT panoramic integral-field<br />
spectrograph operating in the visible<br />
wavelength range.<br />
MUSE has a field of 1x1 arcmin², sampled<br />
at 0.2x0.2 arcsec (Wide Field Mode,<br />
<strong>here</strong>after WFM), and of 7.5x7.5 arcsec²,<br />
sampled at 25 milli-arcsec (Narrow Field<br />
Mode, <strong>here</strong>after NFM), both assisted by<br />
adaptive optics. The simultaneous spectral<br />
range is 0.465-0.93 µm, at a resolution of<br />
R~3000. MUSE couples the discovery<br />
potential of a large imaging device to the<br />
measuring capabilities of a high-quality<br />
spectrograph, while taking advantage of<br />
the increased spatial resolution provided by<br />
adaptive optics. This makes MUSE a<br />
unique and tremendously powerful<br />
instrument <strong>for</strong> discovering and<br />
characterizing objects that lie beyond the<br />
reach of even the deepest imaging surveys.<br />
The most challenging scientific and<br />
technical application, and the most<br />
important driver <strong>for</strong> the instrument design,<br />
is the study of the progenitors of normal<br />
Simulated MUSE deep field. Galaxies are<br />
coloured according to their apparent redshift.<br />
Galaxies detected by their continuum (I AB < 26.7 )<br />
and/or by their Ly α emission (Flux > 3.9 10 -19<br />
erg.s -1 .cm -2 ) are shown.<br />
Sampled area (in arcmin²) and sampled volume<br />
(comoving Mpc 3 ) of MUSE deep fields (red<br />
circles) versus the current Ly α surveys (cross).<br />
nearby galaxies out to redshifts beyond 6.<br />
These systems are extremely faint and can<br />
only be found by their Ly α emission.<br />
MUSE will be able detect these in large<br />
numbers (~15,000) through a set of nested<br />
surveys of different area and depth. The<br />
deepest survey will require very long<br />
integrations (80 hrs each field) and will<br />
reach a limiting flux of 3.9<br />
10 -19 erg.s -1 .cm -2 , a factor 100 better than is<br />
achieved currently with narrow band<br />
imaging. These surveys will<br />
simultaneously address the following<br />
science goals: (i) study of intrinsically faint<br />
galaxies at high redshift, including<br />
determination of their luminosity function<br />
and clustering properties, (ii) detection of<br />
Ly α emission out to the epoch of<br />
reionization, study of the cosmic web, and<br />
determination of the nature of the<br />
reionization, (iii) study of the physics of<br />
Lyman break galaxies, including their<br />
winds and feedback to the intergalactic<br />
medium, (iv) spatially resolved<br />
spectroscopy of luminous distant galaxies,<br />
including lensed objects (v) search of late<strong>for</strong>ming<br />
population III objects, (vi) study<br />
of active nuclei at intermediate and high<br />
redshifts, (vii) mapping of the growth of<br />
MUSE Phase A Executive Summary version 1.0 page 1/4
The median descendant mass of galaxies studied<br />
in various surveys. The deepest ongoing<br />
spectroscopic survey is the VDSS, which selects<br />
galaxies to I AB =26. It samples galaxies to a<br />
redshift of about 4.5 which are the precursors of<br />
current day-galaxies with typical masses of a few<br />
times 10 11 solar masses. MUSE goes a factor 10<br />
deeper and samples the precursors of Milky Way<br />
type galaxies all the way to a redshift of 6.7, the<br />
end of reionization.<br />
dark matter haloes, (viii) identification of<br />
very faint sources detected in other bands,<br />
and (ix) serendipitous discovery of new<br />
classes of objects. Multi-wavelength<br />
coverage of the same fields by MUSE,<br />
ALMA, and JWST will provide nearly all<br />
the measurements needed to answer the<br />
key questions of galaxy <strong>for</strong>mation.<br />
At lower redshifts, MUSE will provide<br />
exquisite two-dimensional maps of the<br />
kinematics and stellar populations of<br />
normal, starburst, interacting and active<br />
galaxies in all environments out to well<br />
beyond the Coma cluster. These will reveal<br />
the internal substructure which is the fossil<br />
record of their <strong>for</strong>mation, and probe the<br />
relationship between supermassive black<br />
holes and their host galaxy. MUSE will<br />
enable massive spectroscopy of the<br />
resolved stellar populations in the nearest<br />
galaxies, outper<strong>for</strong>ming current<br />
capabilities by factors of over 100. This<br />
will revolutionize our understanding of<br />
stellar populations, provide a key<br />
complement to GAIA studies of the<br />
Galaxy, and a preview of what will be<br />
possible with an ELT. Observations of<br />
extended emission-line objects will probe,<br />
e.g., the physics of winds from accretion<br />
disks in young stellar objects, and galactic<br />
fountains, at a spatial resolution that<br />
exceeds that of HST. MUSE will also<br />
allow high-resolution spectroscopic<br />
monitoring of volcanic activity on Io,<br />
studies of the outer planets, and<br />
characterization of small Solar system<br />
bodies.<br />
Examples of southern nearby disk galaxies,<br />
suitable <strong>for</strong> a census of massive stars: NGC45,<br />
NGC55, NGC247, NGC253, NGC300,<br />
NGC7793 (left-right, top-bottom). The DSS<br />
frames subtend a FOV of 5x5arcmin 2 .<br />
The MUSE instrument design is<br />
innovative, and employs an advanced<br />
slicer with a combination of mirrors and<br />
mini-lens arrays. The <strong>for</strong>e-optics includes<br />
an optical derotator, a calibration unit, an<br />
atmospheric dispersion compensator (only<br />
in NFM) and splitting optics. This feeds 24<br />
identical modules: each composed of a<br />
slicer, a high-throughput spectrograph with<br />
a broad response volume phase<br />
holographic grating, and a 4kx4k red<br />
optimized CCD. The instrument achieves a<br />
high throughput with an average of 0.24<br />
end-to-end. The total detector area will<br />
have 403 million pixels. Prototype slicer<br />
MUSE Phase A Executive Summary version 1.0 page 2/4
and volume phase holographic grating<br />
have been manufactured and tested 1 .<br />
High spatial resolution is achieved with<br />
AO. The AO system <strong>for</strong> MUSE is<br />
developed in a companion project, together<br />
with ESO. MUSE will benefit greatly from<br />
the planned adaptive secondary <strong>for</strong> the<br />
VLT, but can also work with an<br />
independent AO system, and has key<br />
science applications even without AO. The<br />
availability of 4 laser guide stars will result<br />
in more than 70% sky coverage at the<br />
galactic pole. The MUSE NFM will<br />
provide a PSF with diffraction limited<br />
core, which will beat HST with up to<br />
10-30% Strehl ratio in the I-z band. In<br />
WFM it will provide 0.3 arcsec resolution<br />
over 1x1 arcmin² even in poor seeing.<br />
MUSE is robust, easy to operate, and<br />
maximizes open shutter time <strong>for</strong> science.<br />
T<strong>here</strong> are no moving parts in the 24<br />
modular spectrographs. The optics is not<br />
sensitive to temperature changes, and the<br />
instrument has only two basic modes<br />
(WFM and NFM). Pointing with 1 arcsec<br />
accuracy is sufficient, and the square field<br />
of view minimizes the need <strong>for</strong> rotation.<br />
Pre-imaging is not required.<br />
Instrument overview at the VLT Nasmyth plat<strong>for</strong>m.<br />
The instrument will be able to reach<br />
extreme depths by means of long total<br />
integrations. This is possible due to the<br />
combination of an optical design that<br />
incorporates field and aperture stops to<br />
control stray light, high throughput, more<br />
than a factor 2 increase in encircled energy<br />
with AO, sufficient spectral resolution in<br />
the red (R=4000@0.93 µm) to allow<br />
observations between the atmospheric OH<br />
lines, with 74% of the red spectral range<br />
free of OH, and an extremely stable<br />
instrument fixed on the Nasmyth plat<strong>for</strong>m.<br />
Preparatory work carried out with<br />
SAURON and FORS demonstrate the<br />
feasibility of long integrations.<br />
Construction of MUSE will include<br />
development of a full data reduction<br />
system, consisting of a pipeline able to<br />
remove the instrument signature in almost<br />
real time, advanced quick look and<br />
vizualisation tools <strong>for</strong> 3D spectroscopy,<br />
advanced data analysis tools <strong>for</strong> 3D datamining,<br />
3D deconvolution, and optimal<br />
datacube summation.<br />
Artist view of MUSE WFM & AO fields of view<br />
1 Results of slicer tests are not available yet (4/2/04)<br />
The overall development strategy<br />
minimizes risk while maximizing scientific<br />
return, by taking advantage of the synergy<br />
MUSE Phase A Executive Summary version 1.0 page 3/4
with the slicer development <strong>for</strong> NIRSPEC<br />
on JWST, through the manufacture and<br />
successful testing of a prototype slicer. A<br />
complete spectrograph unit will be built as<br />
prototype, be<strong>for</strong>e ordering the full set of<br />
24. A dedicated and detailed AIT plan is in<br />
place.<br />
Multiple trade offs were per<strong>for</strong>med in<br />
close collaboration with industry to<br />
minimize the cost of MUSE. The current<br />
design takes full advantage of modularity,<br />
so that the 24 spectrographs can be<br />
manufactured at low unit cost but deliver<br />
high per<strong>for</strong>mance. The total cost of MUSE<br />
will be 9.4 M€ of hardware and 147 FTE.<br />
A 3 year Phase B followed by 4 year phase<br />
C/D will allow delivery to Paranal in mid<br />
2011, perfectly in phase with the launch of<br />
JWST & GAIA, and the completion of<br />
ALMA.<br />
The MUSE Consortium consists of groups<br />
at Lyon (management, system, IFUs),<br />
Ox<strong>for</strong>d (structure, <strong>for</strong>e-optics), Potsdam<br />
(calibration unit, software), Leiden<br />
(adaptive optics), Zurich (financial<br />
In preparation <strong>for</strong> the deep surveys planned <strong>for</strong><br />
MUSE, a pilot programme has been developed<br />
using the SAURON IFU spectrograph. The figure<br />
shows the velocity structure of the z=3.1 Ly α halo<br />
“blob1” in SSA22. The image is colour coded to<br />
show Ly α emission that is red and blue shifted<br />
compared to the sub-mm source.<br />
The JWST/NIRSPEC IFU slicer prototype in<br />
test at CRAL<br />
contribution) and ESO (detectors). The<br />
Consortium has world-leading experience<br />
with pioneering, building, and operating<br />
integral-field spectrographs, including<br />
TIGER, OASIS, SAURON, GMOS-IFU,<br />
PMAS, and, in the future, SINFONI,<br />
SNIFS, and NIRSPEC-IFU. It has unique<br />
expertise in the development of highquality<br />
user-friendly data reduction<br />
software, and leads the Euro3D ef<strong>for</strong>t. The<br />
science team consists of instrumentalists,<br />
observers and theorists, and is carrying out<br />
various preparatory science programs, and<br />
has per<strong>for</strong>med extensive simulations using<br />
state-of-the-art models of galaxies and<br />
galaxy <strong>for</strong>mation to assess the per<strong>for</strong>mance<br />
of MUSE and optimize its design. The<br />
Consortium will provide 134 FTE of ef<strong>for</strong>t<br />
over 7 years, as well as a contribution of<br />
1.75 M€ to the cost of the hardware, and<br />
dedicated AIT facilities built in Lyon.<br />
The Phase A study demonstrates that<br />
MUSE has a very large discovery<br />
potential, outper<strong>for</strong>ms e.g., VIMOS and<br />
FLAMES by factors of well over 100, and<br />
builds and extends the leading role that<br />
Europe has developed in integral-field<br />
spectroscopy. It maximizes the return from<br />
the developments in adaptive optics, will<br />
keep the VLT competitive <strong>for</strong> another<br />
decade by providing an invaluable<br />
complement to ALMA, JWST and GAIA,<br />
and is a key step towards instrumentation<br />
<strong>for</strong> an ELT.<br />
MUSE Phase A Executive Summary version 1.0 page 4/4
MUSE is a 2 nd generation instrument <strong>for</strong> the VLT<br />
Observational Parameters<br />
Spectral range (simultaneous) 0.465-0.93 µm<br />
Resolving power<br />
2000@0.46 µm<br />
4000@0.93 µm<br />
Wide Field Mode (WFM)<br />
Field of view<br />
1x1 arcmin²<br />
Spatial sampling<br />
0.2x0.2 arcsec²<br />
Spatial resolution (FWHM)<br />
0.3-0.4 arcsec<br />
Gain in ensquared energy within 2<br />
one pixel with respect to seeing<br />
Condition of operation with AO 70%-ile<br />
Sky coverage with AO<br />
70% at Galactic Pole<br />
Limiting magnitude in 80h<br />
I AB = 25.0 (R=3500)<br />
I AB = 26.7 (R=180)<br />
Limiting Flux in 80h 3.9 10 -19 erg.s -1 .cm -2<br />
Narrow Field Mode (NFM)<br />
Field of view<br />
7.5x7.5 arcsec²<br />
Spatial sampling<br />
0.025x0.025 arcsec²<br />
Spatial resolution (FWHM)<br />
0.030-0.050 arcsec<br />
Strehl ratio 10-30%<br />
Limiting Flux in 1h 2.3 10 -18 erg.s -1 .cm -2<br />
Limiting magnitude in 1h R AB = 22.3<br />
Instrument<br />
MUSE<br />
Type<br />
Concept<br />
Number of modules 24<br />
Detector<br />
Grating<br />
VPHG<br />
Limiting surface brightness in 1h R AB = 17.3 arcsec -2<br />
Multi Unit IFU<br />
Advanced Slicer<br />
CCD 4096x4096<br />
End-to-end throughput 0.24<br />
Number of pixels 403,000,000<br />
Adaptive Optics<br />
Concept<br />
Ground layer<br />
Sodium Lasers 4<br />
De<strong>for</strong>mable mirror 33x33 actuators<br />
Location<br />
Nasmyth plat<strong>for</strong>m<br />
Dimension 5x3,5x2.5 m 3<br />
Weight<br />
7,800 Kg<br />
Consortium<br />
Artist view of MUSE WFM & AO<br />
fields of view<br />
Schedule<br />
9/2002-2/2004 Phase A<br />
7/2004-5/2007 Phase B<br />
9/2007-2/2011 Phase C/D<br />
End 2011 Commissioning<br />
CRAL (Lyon) - PI<br />
AIP (Potsdam)<br />
ESO (Munich)<br />
ETH (Zurich)<br />
Ox<strong>for</strong>d University<br />
Sterrewachte Leiden
Science Case<br />
Coordinator : R. Bacon<br />
<strong>Institute</strong> : CRAL<br />
Written by : R. Bacon, R. Bower, S. Cabrit, M. Cappellari, M.<br />
Carollo, F. Combes, R. Davies, J. Devriendt, E.<br />
Emsellem, M. Franx, G. Gilmore, B. Guiderdoni,<br />
B. Jungwiert, R. Mc Dermid, S. Morris, O. Le<br />
Fevre, S. Lilly, P. Pinet, M. Roth, M. Steinmetz,<br />
L. Wisotzki, T. de Zeeuw<br />
Reference : MUSE-MEM-SCI-052<br />
Issue : 1.3<br />
Date : 04/02/04<br />
File : Science_case.doc<br />
Distribution : ESO & Consortium<br />
History:<br />
• 0.1 – 03/01/04 – First assembly from science team draft texts<br />
• 0.2 – 12/01/04 – Update from science team<br />
• 0.25 – 13/01/04 – Minor update<br />
• 0.3 – 22/01/04 – Major Update<br />
• 1.0 – 30/01/04 – Almost final<br />
• 1.1 – 01/02/04 – Minor changes<br />
• 1.2 – 02/02/04 – Important polishing (Tim & Richard M)<br />
• 1.3 – 04/02/04 – Last corrections, general intro, phase A release
Title: Science Case<br />
Reference: MUSE-MEM-SCI-052<br />
Issue: 1.3<br />
Date: 04/02/2004<br />
Page: 2/100<br />
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Title: Science Case<br />
Reference: MUSE-MEM-SCI-052<br />
Issue: 1.3<br />
Date: 04/02/2004<br />
Page: 3/100<br />
Documents<br />
Reference documents<br />
AD1 ETC and per<strong>for</strong>mance analysis<br />
AD2 MUSE Top Instrumental Parameters<br />
MUSE-MEM-SCI-051<br />
MUSE-MEM-SCI-016<br />
Acronyms<br />
AD<br />
AO<br />
DF<br />
ESO<br />
ETC<br />
MDF<br />
MUSE<br />
NA<br />
NFM<br />
PSF<br />
R<br />
RD<br />
S/N<br />
SF<br />
UDF<br />
VLT<br />
WFM<br />
Applicable Document<br />
Adaptive Optics<br />
Deep Field<br />
European Southern Observatory<br />
Exposure Time Calculator<br />
Medium Deep Field<br />
Multi Unit Spectroscopic Explorer<br />
Not Applicable<br />
Narrow Field Mode<br />
Point Spread Function<br />
Spectral Resolving Power<br />
Reference Document<br />
Signal over noise<br />
Shallow Field<br />
Ultra Deep Field<br />
Very Large Telescope<br />
Wide Field Mode
Title: Science Case<br />
Reference: MUSE-MEM-SCI-052<br />
Issue: 1.3<br />
Date: 04/02/2004<br />
Page: 4/100<br />
Documents.................................................................................................................................. 3<br />
Reference documents .............................................................................................................3<br />
Acronyms ................................................................................................................................... 3<br />
1. Introduction ........................................................................................................................ 5<br />
2. Formation of galaxies......................................................................................................... 6<br />
2.1. Introduction ................................................................................................................ 6<br />
2.2. High redshift Lyman alpha emitters......................................................................... 11<br />
2.3. Fluorescent emission and the cosmic web ............................................................... 20<br />
2.4. Reionization ............................................................................................................. 24<br />
2.5. Feedback processes and galaxy <strong>for</strong>mation............................................................... 27<br />
2.6. Ultra-deep survey using strong gravitational lensing............................................... 32<br />
2.7. Resolved spectroscopy at intermediate redshift....................................................... 35<br />
2.8. Sunyaev-Zeldovich effect ........................................................................................ 39<br />
2.9. Late <strong>for</strong>ming population III objects ......................................................................... 40<br />
2.10. Active galactic nuclei at intermediate and high redshifts .................................... 42<br />
2.11. The development of dark matter haloes ............................................................... 44<br />
2.12. Merger rate ........................................................................................................... 45<br />
2.13. Survey strategy..................................................................................................... 46<br />
2.14. A pan-chromatic view of galaxy <strong>for</strong>mation ......................................................... 50<br />
3. Nearby galaxies................................................................................................................ 53<br />
3.1. Introduction .............................................................................................................. 53<br />
3.2. Supermassive black holes in nearby galaxies .......................................................... 53<br />
3.3. Kinematics and stellar populations .......................................................................... 57<br />
3.4. Interacting galaxies .................................................................................................. 62<br />
3.5. Star <strong>for</strong>mation in nearby galaxies............................................................................. 63<br />
4. Stars and resolved stellar populations .............................................................................. 66<br />
4.1. Introduction .............................................................................................................. 66<br />
4.2. Early stages of stellar evolution ............................................................................... 66<br />
4.3. Massive spectroscopy of stellar fields: our Galaxy and the Magellanic Clouds...... 71<br />
4.4. Massive spectroscopy of stellar fields: The Local group and beyond ..................... 76<br />
5. Solar system ..................................................................................................................... 89<br />
5.1. Introduction .............................................................................................................. 89<br />
5.2. Galilean Satellites and Titan surfaces ...................................................................... 89<br />
5.3. Surface heterogeneities of the small bodies ............................................................. 91<br />
5.4. Temporal changes in Jupiter, Saturn, Uranus and Neptune ..................................... 92<br />
6. Serendipity ....................................................................................................................... 94<br />
7. Instrument requirements................................................................................................... 95<br />
7.1. "Formation of galaxies" science case....................................................................... 96<br />
7.2. "Nearby galaxies" science case ................................................................................ 96<br />
7.3. "Stars and resolved stellar populations" science case .............................................. 96<br />
7.4. "Solar system" science case ..................................................................................... 96<br />
8. Competitiveness ............................................................................................................... 97<br />
8.1. Introduction .............................................................................................................. 97<br />
8.2. Wide field IFU ......................................................................................................... 98<br />
8.3. High spatial resolution IFU...................................................................................... 99
Title: Science Case<br />
Reference: MUSE-MEM-SCI-052<br />
Issue: 1.3<br />
Date: 04/02/2004<br />
Page: 5/100<br />
1. Introduction<br />
This document presents the science case <strong>for</strong> the Multi Unit Spectroscopic Explorer (MUSE).<br />
Four scientific areas have been explored: <strong>for</strong>mation of galaxies, nearby galaxies science, stars<br />
and resolved stellar populations and solar system applications. The <strong>for</strong>mation of galaxies<br />
(section 2) is the most challenging scientifically and technically, and has been used as the<br />
most important driver <strong>for</strong> the instrument design. It has been developed in depth, using as<br />
much as possible quantitative estimators taken either from the literature or from extensive<br />
numerical simulations. The nearby galaxy science (section 3) and the stars and stellar<br />
population (section 4) have been significantly enhanced with respect to the pre-phase A<br />
document. We have also added a new section on solar system science (section 5), although it<br />
has not been considered as a driver <strong>for</strong> the instrument.<br />
Apart from these science goals, we stress the large potential of serendipitous discoveries of<br />
MUSE (section 6). We then summarize instrument requirements in section 7 and discuss<br />
MUSE competitiveness with respect to existing or planned similar facilities in section 8.
2. Formation of galaxies<br />
Title: Science Case<br />
Reference: MUSE-MEM-SCI-052<br />
Issue: 1.3<br />
Date: 04/02/2004<br />
Page: 6/100<br />
2.1. Introduction<br />
The advent of 10-m class telescopes and high throughput instrumentation has fully opened a<br />
new research area in astronomy: the study of the overall populations of galaxies at high<br />
redshifts. At redshift 3, when the universe was 15 % of its current age, and the typical<br />
separations between objects were 1/4 of the current values, the galaxies that are unveiled by<br />
the deep surveys like the HDFs seem to be quite different from the local, giant galaxies of the<br />
Hubble sequence.<br />
W<strong>here</strong>as, in the early nineties, only extreme objects were known in the distant universe 1 ,<br />
recent deep surveys based on broad-band magnitude selection can now collect large<br />
populations of galaxies from z=2 to z=3–4 (e.g., Steidel et al 1996, 1999, 2003, Madau et al.<br />
1996). The strong spectral features of the so-called Lyman-break galaxies allow us to derive<br />
fairly accurate photometric redshifts from precise photometry. Hence deep ground-based and<br />
HST photometry can be used to sample and study fainter galaxies than can be observed<br />
spectroscopically. The ground-based studies have produced a wealth of in<strong>for</strong>mation which we<br />
are still slowly digesting: the correlation function of Lyman break galaxies (Giavalisco et al.<br />
1997), the existence of galactic size winds (Franx et al 1998, Pettini et al 1998, Shapley et al<br />
2003), the interaction of winds with the IGM, the photoionizing flux (Steidel et al, 1998), the<br />
rest-frame optical properties of Lyman break galaxies, their optical emission lines, etc. These<br />
pioneering studies are now being extended to larger samples: e.g., VDSS survey (Le Fevre et<br />
al, 2003), Cosmos survey (Scoville et al, 2003), in order to obtain better statistics, and to<br />
describe the environmental dependencies. These large surveys will yield the z=3–4 equivalent<br />
of the 2DF or Sloan survey at much lower redshift.<br />
However it is clear that the current ongoing and planned surveys have intrinsic limitations that<br />
follow naturally from the capabilities of current telescopes and instruments. In order to obtain<br />
large enough samples in a reasonable time, they use integration times of typically 2 hours, and<br />
sample galaxies to a magnitude of R AB =25.5 (e.g., Steidel et al 1999), with incompleteness<br />
setting in above that limit. The consequence of this limit is that we study only the bright end<br />
of the luminosity function, and probe only a factor 10 in luminosity under the brightest<br />
objects, in a regime w<strong>here</strong> the luminosity function is still rising. Furthermore, the galaxies are<br />
a very biased population of the full population, with a very strong correlation function<br />
(Giavalisco et al 1998). Even though their number density is similar to that of nearby normal<br />
galaxies (Steidel et al 1996), they are likely not the progenitors of the latter. The clustering<br />
strength is expected to depend on the number density of the halos in which galaxies reside.<br />
Assuming a simple relation between galaxy brightness and halo mass, we expect that faint<br />
galaxies cluster less than bright galaxies, and that faint galaxies are the true progenitors of<br />
normal nearby galaxies. As Lyman-break galaxies seem to be the progenitors of current giant<br />
elliptical galaxies that reside in clusters (Baugh et al 1998), we need to go a factor of 10<br />
deeper in order to access the galaxies that are the progenitors of normal galaxies.<br />
1 Active nuclei with very strong emission lines
Title: Science Case<br />
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The HDF studies actually go deeper but are limited to a small number of objects. For instance,<br />
with magnitude limits roughly corresponding to R AB 5 have R AB
However, the great disadvantage of<br />
the search by narrow-band filters is<br />
that these achieve lower spectral<br />
resolution, and hence less contrast<br />
between the emitter and the night<br />
sky. Furthermore, bright sky lines<br />
that are abundant in the red make<br />
narrow band searches extremely<br />
inefficient over most of the<br />
wavelength range except <strong>for</strong> a few<br />
gaps. Finally, objects selected by<br />
narrow band surveys still need<br />
spectroscopic follow-up, and have<br />
generally large interloper fractions.<br />
At the depth that we wish to reach<br />
<strong>here</strong>, spectroscopic follow-up by<br />
itself would be very time<br />
consuming, and hence the only<br />
strategy which can work is one<br />
w<strong>here</strong> the galaxies are selected<br />
from the spectroscopy itself. The<br />
efficiency of this search technique<br />
is higher, as long as we have an<br />
efficient spectrograph with wide<br />
field of view. The key element <strong>for</strong><br />
Title: Science Case<br />
Reference: MUSE-MEM-SCI-052<br />
Issue: 1.3<br />
Date: 04/02/2004<br />
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MUSE limiting flux<br />
The limiting flux quoted in the following sections are <strong>for</strong><br />
an unresolved source and S/N=5. Approximately 50%<br />
of source flux is recovered by integration over 0.6x0.6<br />
or 0.8x0.8 arcsec², depending on seeing conditions and<br />
use of AO. Assumptions, results and analysis are<br />
presented in the “ETC and per<strong>for</strong>mance analysis”<br />
document (RD1).<br />
Integ. Line magnitude I AB<br />
Time Flux Full R R/20<br />
SF 1 h 50.0 22.2 23.9<br />
MDF 10 h 11.0 23.9 25.5<br />
DF 80 h 3.9 25.0 26.7<br />
UDF 80 h 1.3 26.2 27.9<br />
Notes:<br />
• Unless explicitly specified, flux and magnitude<br />
are average value in the 0.6-0.93 µm<br />
wavelength range<br />
• Flux is in 10 -19 erg.s -1 .cm -2 units<br />
• Magnitude is given <strong>for</strong> full (R~3000) or low<br />
(R~150) spectral resolution<br />
• SF is without AO and median seeing conditions<br />
• MDF, DF and UDF are with AO and median<br />
seeing conditions<br />
• UDF assumes a factor 3 gain by lensing<br />
MUSE is that it is a giant Integral Field Unit (IFU) spectrograph, which can sample a full 1x1<br />
arcmin 2 field from 4650 Å to 9300 Å. Using an IFU spectrograph is by far the most efficient<br />
way to search <strong>for</strong> emission line objects. Furthermore, we optimize MUSE by incorporating a<br />
partial Adaptive Optics system, which enhances the efficiency by another factor of 2. The<br />
depth that can be reached with this instrument is a flux limit of 3.9 10 -19 ergs.s -1 cm -2 , <strong>for</strong> Ly α<br />
emitters between z=2.8 and z=6.7, in an integration time of 80 hours. This is a factor of 30<br />
deeper than what is currently achieved with ground-based facilities! The number of galaxies<br />
detected at this level is unknown, but we can extrapolate from previous surveys, or use model<br />
predictions. The first results of the narrow band surveys (e.g. Rhoads et al.) indicate quite<br />
steep counts <strong>for</strong> the Ly α emission line flux (in number per arcmin 2 and unit redshift) at<br />
redshifts 3.4, 4.8 and 5.7: N(>f)∝f -2 between 2 10 -16 ergs.s -1 cm -2 and 1.5 10 -17 ergs.s -1 cm -2 ,<br />
which, if extrapolated to 3.9 10 -19 ergs.s -1 cm -2 would indicate a factor 1500 more sources. The<br />
current observed densities of a few to a few 0.1 sources arcmin -2 (∆z) -1 (between z~3.4 and<br />
5.7) will be trans<strong>for</strong>med into several 100 sources arcmin -2 (∆z) -1 . Moreover, since it turns out<br />
that the Ly α luminosity function seems to be quite constant, this gain will simultaneously<br />
mean more objects with fainter luminosities and more remote distances.<br />
If we take this rough extrapolation at face value, we will find 300–1000 Ly α emitters at<br />
2.8
Title: Science Case<br />
Reference: MUSE-MEM-SCI-052<br />
Issue: 1.3<br />
Date: 04/02/2004<br />
Page: 9/100<br />
integrate 4 times longer 2 because it does not have the AO unit. We could only observe<br />
continuum-selected objects, of which only 25% have sufficiently strong Ly α . Hence we would<br />
find 75–250 Ly α objects in 320 hours of integration time, 0.2–0.8 galaxy per hour, more than<br />
a factor of 10 lower. Hereafter, we will use a more refined model of galaxy <strong>for</strong>mation which<br />
gives more conservative results (N(>f)∝f -1.7 ) below 1.5 10 -17 ergs.s -1 cm -2 . According to this<br />
model, MUSE will detect 300 objects in an 80-hour integration, which is in the low end of the<br />
above-mentioned estimate. VIMOS would also detect fewer objects. Hence these comparisons<br />
are fairly independent of the details of the galaxy population.<br />
At the time when MUSE comes on the VLT, 8-10 m class telescopes will have been in<br />
operation <strong>for</strong> 15 years. Hence the "quick-and-easy" projects will have been done already, and<br />
the telescopes will have to be operated in a new way to push the frontier. W<strong>here</strong>as the largest<br />
survey being carried out now takes on the order of 50 nights, programs of even larger size will<br />
be more typical by 2011. Hence we should think in programs which can be done in many<br />
100's of hours of integration time, not 100 hours 3 .<br />
In the following we discuss the science in the field of galaxy <strong>for</strong>mation that can be done with<br />
MUSE in 1000 hours 4 . This is not meant to be exhaustive, nor meant to be a claim by the<br />
MUSE team that they reserve the right to do this all by themselves. It shows applications of<br />
MUSE, whether done by the MUSE team, or the community. The survey is a staggered<br />
survey using different depths and area coverage. It uses exclusively the WFM and AO<br />
capabilities, except <strong>for</strong> the shallow survey which does not require AO. It consists of:<br />
• Shallow survey (SF), reaching a flux density of 5. 10 -18 erg.s -1 .cm -2 , and an area coverage<br />
of 200 arcmin 2 .<br />
• Medium deep survey (MDF), reaching a flux density of 1.1 10 -18 erg.s -1 .cm -2 , and an<br />
area coverage of 40 arcmin 2 .<br />
• Deep survey (DF), reaching a flux density of 3.9 10 -19 erg.s -1 .cm -2 , and an area coverage<br />
of 3 arcmin 2<br />
• Ultra deep survey (UDF), reaching a flux density of 1.3 10 -19 erg.s -1 .cm -2 <strong>for</strong> 0.6 arcmin 2 ,<br />
using lensing clusters.<br />
These numbers are chosen based on our current knowledge and simulations. It is likely that<br />
the strategy will evolve with time. With the above-mentioned estimates based on current<br />
surveys, it is <strong>for</strong>eseen that MUSE will have detected more than about 15,000 2.8
The science that can be done with<br />
MUSE is very broad. It opens up a<br />
completely new regime <strong>for</strong> optical<br />
spectroscopy, both at high redshifts,<br />
and at low redshift. At high redshifts,<br />
we can finally sample the progenitors<br />
of normal galaxies like the Milky Way.<br />
We can measure the strength of the<br />
correlation function as a function of<br />
luminosity of the galaxy. We can<br />
finally sample galaxies out to z=6.7,<br />
beyond the regime w<strong>here</strong> the universe<br />
becomes optically thick shortward of<br />
Ly α . We can identify the nature of<br />
objects which produce the last phase of<br />
re-ionization. We can do the<br />
equivalents of the studies done now <strong>for</strong><br />
very bright galaxies at z=3, study the<br />
impact of giant galactic winds on the<br />
IGM, study the environments of<br />
AGN 5 . We get (<strong>for</strong> free) resolved<br />
Title: Science Case<br />
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spectroscopy of bright Lyman break galaxies at z=3, and, obviously, at lower redshifts. In<br />
short, MUSE opens up a full area of research that would be inaccessible otherwise.<br />
In the next sections we discuss in more detail the science goals which can be addressed<br />
simultaneously with these surveys. It is organized as follows: In 2.2 we discuss the high<br />
redshift Ly α emitters, including determination of their luminosity function and clustering<br />
properties. In 2.3 we consider the study of the fluorescent emission and the cosmic web and<br />
in 2.4 the nature of the last phase of the reionization. In 2.5 feedback processes to the<br />
intergalactic medium are studied in relation with the physics of Lyman break galaxies. In 2.6<br />
we take advantage of strong lensing to improve the depth of the survey and to per<strong>for</strong>m<br />
spatially resolved spectroscopy of luminous distant galaxies. In 2.7 we extend this study of<br />
spatially resolved galaxies to non lensed surveys at intermediate redshift. In 2.8 we discuss<br />
follow-up observations of Sunyaev-Zeldovich cluster and in 2.9 we propose to use MUSE to<br />
search <strong>for</strong> late-<strong>for</strong>ming population III objects. In 2.10 the study of active nuclei at<br />
intermediate and high redshifts is presented and in 2.11 the mapping of the growth of dark<br />
matter haloes. Measure of the merger rate is discussed in 2.12. Finally the survey strategy is<br />
presented in 2.13, and the complementarities of MUSE with JWST, ALMA and other<br />
facilities are discussed in 2.14.<br />
References<br />
Ajiki et al. 2003, AJ, 126, 2091<br />
Ajiki et al. 2002, ApJ, 576, 25<br />
Baugh et al 1998, ApJ, 498, 504<br />
Cowie & Hu 1998, AJ, 115, 1319<br />
Figure 2-1: Sampled area (in arcmin²) and sampled<br />
volume (comoving Mpc 3 ) of MUSE deep fields (red<br />
circles) versus the current Ly α surveys<br />
(cross) discussed in Table 2-1 (section 2.2).<br />
5 If every L* galaxy has a black hole, than this phase may have been common, although short lived
Title: Science Case<br />
Reference: MUSE-MEM-SCI-052<br />
Issue: 1.3<br />
Date: 04/02/2004<br />
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Ellis et al. 2001, ApJ, 560, 119<br />
Franx et al 1997, ApJ, 486, 75<br />
Giavalisco et al. 1998, ApJ; 503, 543<br />
Hu & McMahon 1996, ApJ, 459, 53<br />
Hu et al. 1999, ApJ, 522, 9<br />
Hu et al. 2002, ApJ, 576, 99<br />
Kodaira et al. 2003, PASJ, 55, 17<br />
Kudritzki et al. 2000, ApJ, 536, 19<br />
Le Fevre et al, 2003, The Messenger 111<br />
Madau et al, 1996, MNRAS, 283, 1388<br />
Pettini et al 1998, ApJ, 508, 539<br />
Rhoads et al. 2000, ApJ, 545, 85<br />
Rhoads et al. 2003, AJ, 125, 1006<br />
Scoville et al, 2003 (http://www.astro.caltech.edu/cosmos)<br />
Shapley et al., 2001, ApJ, 562, 37<br />
Stanway et al. 2004, ApJ, submitted, astroph/0312459<br />
Shapley et al 2003, ApJ, 588, 65<br />
Stiavelli et al. 2001, ApJ, 561, 37<br />
Steidel et al, 1996, ApJ, 462, L17<br />
Steidel et al, 1999, ApJ, 519, 1<br />
Steidel et al, 2003, ApJ, 592, 728<br />
Steidel et al, 2001, ApJ, 546<br />
Steidel et al, 1998, ApJ, 508, 539<br />
Taniguchi et al. 2003, ApJ, 585, 97<br />
Venemans et al. 2002, ApJ, 569, 11<br />
Weymann et al, 1998, 505, L95<br />
2.2. High redshift Lyman alpha emitters<br />
The main target of the MUSE surveys is to find and study the building blocks of the local,<br />
normal galaxies such as our Milky Way, at an epoch when the universe was typically 1 Gyr<br />
old. The observation of such objects will be of great value to clarify the way galaxies <strong>for</strong>m. In<br />
the commonly accepted hierarchical picture, mass assembling is a long-timescale process, that<br />
starts early and goes on till the present time. Making the census of big and small objects in the<br />
early universe, when the cosmic age was 1 Gyr, and studying their properties, will set strong<br />
constraints on detailed models of hierarchical galaxy <strong>for</strong>mation. In this prospect, the specific<br />
questions which one wants to address by studying this population of objects are the following:<br />
how did galaxies like our Milky Way assemble from small fragments? What are the stellar<br />
and gaseous masses of these fragments? What are the masses of the dark matter haloes they<br />
are hosted in? What are their typical star <strong>for</strong>mation histories?<br />
The issue is to find an observational signature that is as efficient as possible to identify highredshift<br />
low-mass objects. In section 2.1, we have argued that high-redshift low-mass objects<br />
should be searched <strong>for</strong> in an emission-line survey, and that MUSE is a unique instrument to<br />
reach this goal. Hereafter, we try to refine our estimates of the MUSE efficiency with respect<br />
to current surveys, and we discuss the type of statistical studies that could be achieved.
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A search <strong>for</strong> Ly α emission was the<br />
first proposed method to find highredshift<br />
<strong>for</strong>ming galaxies (also<br />
called "primeval galaxies", a term<br />
not in use anymore). Partridge &<br />
Peebles (1967) predicted that the<br />
monolithic collapse of a giant<br />
elliptical galaxy should produce a<br />
Ly α luminosity of 10 45 erg/s, which<br />
would be observed at a typical flux<br />
level of 10 -15 erg.s -1 .cm -2 . In spite<br />
of many systematic searches, such<br />
objects have not been observed,<br />
and only deeper surveys, at the<br />
current sensitivity of a few times<br />
10 -17 erg.s -1 .cm -2 , have unveiled a<br />
population of Ly α emitters with<br />
luminosities 10 42-43 erg/s. Such<br />
luminosities are expected in the<br />
hierarchical picture. However, the<br />
failure to find very strong Ly α<br />
emission is probably caused by<br />
many effects: the line is partly<br />
decreased by the photospheric<br />
absorption line in post-starburst<br />
stellar populations (Valls-Gabaud<br />
1993). Furthermore it can be<br />
scattered out to large distances by<br />
resonant scattering, reducing the<br />
surface brightness. Finally, any<br />
z ∆z Area<br />
arcm<br />
in 2<br />
Flux limit<br />
erg/s/cm 2<br />
Density<br />
arcmin -<br />
2 ∆z -1 Reference<br />
2.42 0.14 1260 2x10 -16 0.49 Stiavelli et al. 2001<br />
3.13 0.04 50 1.5x10 -17 4.0 Kudritzki et al.<br />
2000<br />
3.44 0.065 46 2x10 -17 3.3 Cowie and Hu<br />
1998<br />
3.44 0.065 46 1.5x10 -17 4.2 Hu et al. 1998<br />
3.72 0.22 132 3.9x10 -17 (?) 0.21 Fujita et al. 2003<br />
4.5 0.07 1160 2x10 -17 1–1.5 Rhoads et al. 2000,<br />
Rhoads &<br />
Malhotra 2001<br />
4.54 0.053 24 1.5x10 -17 4.2 Hu et al. 1998<br />
4.86 0.05 543 1.1x10 -17 (?) 3.2 Ouchi et al. 2003<br />
5.7 0.1 707 1.6x10 -17 0.11–<br />
0.15<br />
Rhoads &<br />
Malhotra. 2001,<br />
Rhoads et al. 2003<br />
5.7 0.1 720 1.4x10 -17 (?) 0.28 Ajiki et al. 2003<br />
5.7 0.1 918 2x10 -17 0.3 Hu et al. 2004<br />
5.7 1 0.029 1.9x10 -18 34 Ellis et al. 2001<br />
Table 2-1: A sampling of the observed surface density found <strong>for</strong><br />
Ly α emitters sorted out by redshift. The estimate of surface density<br />
is typically based on 10–100 objects, with Poisson error bars at<br />
the 10–30 % level (at 1 σ). The flux limits labelled by a (?) have<br />
been derived from the luminosities of the published sources. Only<br />
candidate Ly α galaxies are found by most papers, and some<br />
authors suggest correction factors significantly lower than 1. The<br />
last line corresponds to an estimate based on a single lensed<br />
source. This value is quite uncertain, but it illustrates how common<br />
these faint objects should be.<br />
dust in the neutral, scattering gas will reduce the escaping fraction of photons drastically<br />
(Charlot & Fall 1991, 1993). The outflows that are seen in nearby starbursts, and distant<br />
galaxies affect the direction, and kinematic structure of Ly α photons. However, it is now clear<br />
that galactic winds and massive outflows, as well as infalling material, strongly help Ly α<br />
photons avoid absorption through resonant scattering in the dusty medium, and escape from<br />
the galaxies (Lequeux et al. 1995). As a consequence, the question remains open, and only<br />
more detailed surveys will set stronger constraints.<br />
Table 2-1 gathers the results of the main narrow-band Ly α surveys. The current surveys on a<br />
fraction of a square degree fields in thin redshift slices (typically ∆z =0.05) obtain a few ten to<br />
a few hundred candidates that need subsequent spectroscopic confirmation. The density of<br />
candidates is typically a few arcmin -2 per redshift interval of unity. For instance, at a typical<br />
flux level of 2 10 -17 erg s -1 cm -2 , the Large Area Lyman Alpha survey (LALA), has 225<br />
candidates in 0.31 deg 2 at z=4.5, obtained after 30h of exposure time (in five narrow-band<br />
filters), and the confirmation of each object requires about 1h of LRIS exposure time at the
Keck Telescope (Rhoads et al.<br />
2000). The confirmation rate of<br />
true Ly α galaxies, although<br />
based on very poor statistics,<br />
only amounts to 30 to 50 %,<br />
and leads to an effective<br />
observing cost of 2.3–3.8 h of<br />
observing time per confirmed<br />
object. With the HST, the<br />
Grism ACS Program <strong>for</strong><br />
Extragalactic Science<br />
(GRAPES, Malhotra et al.),<br />
and the ACS Pure Parallel<br />
Lyman α Emission Survey<br />
(APPLES, Rhoads et al.) at a<br />
typical spectral resolution<br />
R=100, and a flux level of 6 10 -<br />
18 erg s -1 cm -2 , are <strong>for</strong>eseen to<br />
give respectively about 63-400<br />
Ly α galaxies, and 1000 Ly α<br />
galaxy candidates at 4
galaxies without ambiguity.<br />
W<strong>here</strong>as redshifts based on a<br />
single emission line are<br />
generally uncertain, the Ly α<br />
line can be identified by the<br />
asymmetric line profiles that<br />
are found in almost all cases<br />
(see, e.g., Franx et al 1997,<br />
Weyman et al 1998). These are<br />
caused by a combination of<br />
effects: line broadening by<br />
large-scale flows, and resonant<br />
scattering, and absorption by<br />
outflowing neutral material.<br />
The first authors showed how<br />
at a spectral resolution R=1500<br />
the asymmetry could be<br />
detected in a weak object, and<br />
could be distinguished from<br />
redshifted [OII] 3727. The<br />
structure of the outflows can<br />
be studied and lower limits <strong>for</strong><br />
the SFR can be derived from<br />
the detailed study of the line<br />
profiles. More in<strong>for</strong>mation on<br />
morphology given by subarcsec<br />
spatial resolution may<br />
unveil signs of merging and<br />
interaction, which are expected<br />
in the paradigm of hierarchical<br />
<strong>for</strong>mation.<br />
To estimate the efficiency of<br />
MUSE, we produce<br />
predictions of the number<br />
counts of Ly α emitters that<br />
will be found in MUSE deep<br />
Any<br />
continuum<br />
magnitude<br />
Title: Science Case<br />
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Flux Limit (ergs/s/cm2)<br />
z<br />
2.8-6.7 2.8-4 4-6.7<br />
CURRENT 2x10 -17 5.3 4.5 0.8<br />
SHALLOW 5x10 -18 43.1 35.6 7.5<br />
MEDIUM<br />
DEEP<br />
1.1x10 -18 166 102 64<br />
DEEP 3.9x10 -19 287 152 135<br />
ULTRA<br />
DEEP<br />
1.3x10 -19 386 198 188<br />
I AB >26.7 DEEP 3.9x10 -19 275 141 134<br />
I AB >29 DEEP 3.9x10 -19 108 35 73<br />
I AB >31 DEEP 3.9x10 -19 16.2 2.7 13.5<br />
Table 2-2: Predictions of the number densities (per arcmin 2 ) of Ly α<br />
emitters in two redshift ranges according to the GalICS model<br />
(Hatton et al. 2003 and other papers of the series). The Ly α escape<br />
fraction is set at the value of 0.15, in order to fit the current surveys at<br />
2.10 -17 erg/s/cm 2 and z=3.4, w<strong>here</strong> the statistics is good enough (3.3<br />
Ly α emitters arcmin -2 (∆z) -1 ). The fraction of objects lost due to<br />
coincidence of Ly α and OH emission has been taken into account.<br />
Flux Limit 2.8
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observations <strong>for</strong> the local and z=3 universe. They correspond to a flat or decreasing cosmic<br />
SFR at z>4, <strong>for</strong> which very little data is available. Their predictions should be considered as<br />
quite conservative lower values since it is pretty possible that the cosmic SFR strongly<br />
increases at z>4, maybe by a factor 10 as suggested by the analysis of Lanzetta et al. (2002).<br />
Ultimately, the solution to clarify this point is to obtain the data with MUSE.<br />
We assume that Ly α photons are produced by ionized regions (case B recombination). In such<br />
models, the description of the Ly α line is particularly delicate, because of the existence of<br />
stellar absorption after a starburst (due to A stars), and of resonant scattering. Only a small<br />
fraction of the emitted Ly α photons should escape from a homogeneous dusty medium.<br />
Nevertheless, Ly α emission is observed in local objects (such as Blue Compact Dwarfs) and<br />
high-redshift galaxies (Ly-break galaxies and Ly α galaxies found in wide-field, narrow-band<br />
surveys). It is thought that the existence of an expanding medium prevents Ly α photons from<br />
resonant scattering, and produces characteristic P-Cygni profiles. T<strong>here</strong> is no simple<br />
modelling of such a process. At the current stage, we make predictions <strong>for</strong> two different<br />
models: (i) a fixed escape fraction f esc which would correspond to «holes» in the gas and dust<br />
distribution, and that is normalised in order to reproduce number counts obtained by current<br />
surveys; (ii) absorption in a dusty<br />
medium without resonant scattering<br />
(let’s say, if the velocity of the<br />
expanding medium is high enough to<br />
completely hamper resonant scattering).<br />
A more realistic model is clearly needed.<br />
It is <strong>for</strong>eseen that the interpretation of<br />
current Ly α surveys and the preparation<br />
of MUSE will foster theoretical activity<br />
on this point.<br />
T<strong>here</strong> is very little observational<br />
constraint on the value of the Ly α escape<br />
fraction. Steidel et al. (2001) give f esc ≥<br />
0.07–0.1 from Ly-break galaxy spectra,<br />
but it is very likely that stellar<br />
populations at higher redshifts are<br />
younger, less chemically evolved and<br />
less dusty. We choose to fix f esc in order<br />
to reproduce current Ly α surveys. At<br />
z=3.4, the observed surface density of<br />
reasonable confirmed objects at the<br />
2.10 -17 erg.s -1 .cm -2 flux level is 12,000<br />
deg -2 (∆z) –1 , that is, 3.3 arcmin -2 (∆z) –1 .<br />
This is obtained with f esc =0.15. This<br />
number appears reasonable in the light<br />
of more specific studies that take into<br />
account plausible values <strong>for</strong> the covering<br />
factor and metallicity (e.g. Haiman &<br />
Spaans 1999). The decrease of<br />
Figure 2-2: Predictions of faint galaxy counts in<br />
three redshift bins with the GalICS model. The<br />
escape fraction <strong>for</strong> Ly α photons is fixed in order to<br />
reproduce the current counts at a flux limit of<br />
2.10 -17 erg.s -1 .cm -2 in a redshift slice at z=3.4. Solid<br />
dots show the results of the recent surveys taken<br />
from Table 2-1 (error bars are only Poissonian).<br />
The effect of clustering on the cosmic variance<br />
appears from the scatter of the points. The model<br />
seems to scale fairly with redshift. The open<br />
triangle shows an estimate based on a single lensed<br />
source at a redshift z=5.7. The MUSE Deep Field<br />
flux limit is also shown
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metallicity expected at higher and higher redshifts should help increase this escape fraction,<br />
but we do not attempt to model this effect. In any case, it will produce more detectable<br />
sources.<br />
At the 2 10 -17 level, our standard GalICS model predicts a surface density of 2855 deg -2 (∆z) -1<br />
at z=4.5, and 444 deg -2 (∆z) –1 at z=5.7, in reasonable agreement with the data of the LALA<br />
survey (3600—5400 deg -2 (∆z) –1 at z=4.5 and 390–540 /deg 2 /∆z at z=5.7, see Rhoads et al.<br />
2000, Rhoads and Malhotra 2001, Rhoads et all. 2003), provided the uncertainty on the<br />
confirmation rate, but on the conservative side. The SUBARU survey at the 1.4 10 -17 flux<br />
level finds 1000 candidates deg -2 (∆z) -1 at z=5.7 (Ajiki et al. 2003) and argue that they are<br />
bona-fide Ly α emitters (although only 1/10 th is confirmed spectroscopically). The slope of the<br />
faint counts predicted by our models is N(>f) ∝ f -1.7 , more conservative than the estimate<br />
based on a rough extrapolation of the current data N(>f) ∝ f -2 .<br />
As shown in Table 2-2, MUSE will be<br />
able to increase significantly the<br />
detection rate of the most interesting<br />
objects at z>4. At 2.8
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6x10 -18 flux level of GRAPES, GalICS predicts about 85 galaxies at z>4 in the 11.3 arcmin 2<br />
field of view of the ACS, <strong>for</strong> about 60h of observing time (at a cost of 0.7 h per galaxy), a<br />
projection that is quite sensitive to the flux threshold, but lies on the conservative side of the<br />
estimates made by the GRAPES team. Of course, if it turns out that GRAPES gets more<br />
objects, the efficiency of MUSE will be correspondingly increased. In any case, this makes<br />
MUSE deep fields significantly more efficient<br />
than current narrow-band surveys, and even<br />
than HST deep surveys, to find bona-fide faint<br />
Ly α emitters.<br />
Moreover, according to these models, most of<br />
the objects detected by MUSE at 4
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and the SFR history within these objects. Under the assumption that 1 M sun /yr produces 10 42<br />
erg/s (Kennicutt 1988), and that only 15 % of these photons actually escape from the galaxies,<br />
the MUSE Ly α luminosity function will probe objects that emit 10 41 erg/s at z~5.7 (currently<br />
it gets down to 5 10 42 erg/s, Ajiki et al. 2003), that translates into SFRs lower than 1 M sun /yr,<br />
up to objects which emit 10 43 erg/s and have more than 100 M sun /yr.<br />
Figure 2-4: The median descendant mass of<br />
galaxies studied in various surveys. We used the<br />
GALICS simulations to construct a set of<br />
simulated galaxies at cosmological distances, and<br />
we applied the selection criteria appropriate to<br />
each of the surveys. For each selected galaxy the<br />
simulation was used to follow the merging tree<br />
and to derive the stellar mass at z=0. This is<br />
called the descendant mass. The deepest ongoing<br />
spectroscopic survey is the VDSS, which selects<br />
galaxies to I AB =26. It samples galaxies to a<br />
redshift of about 4.5 which are the precursors of<br />
current day-galaxies with typical masses of a few<br />
times 10 11 solar masses. MUSE goes a factor 10<br />
deeper and samples the precursors of Milky Way<br />
type galaxies all the way to a redshift of 6.7, the<br />
end of reionization.<br />
Figure 2-5: Predictions <strong>for</strong> the 2D 2-point<br />
correlation function with the GalICS model.<br />
The line shows the values measured in the<br />
SUBARU Deep Field at a flux level of 1.1 10 -17<br />
erg/s/cm 2 by Ouchi et al. (2003) in a thin<br />
redshift slice z=4.86±0.03, maybe dominated<br />
by a large-scale structure. The green dots show<br />
the predictions at this flux level in the redshift<br />
bin z=4.67
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Other properties can be measured <strong>for</strong> subsamples of the MUSE sources with complementary<br />
instruments such as JWST and ALMA, and subsequently SKA, to get a complete view on the<br />
extinction, gas and dust content (through the redshifted H α , CO, and HI 21 cm lines, and the<br />
submm/mm continuum emission (see more details in section 2-14 ).<br />
Even quite conservative assumptions on the expected sources demonstrate that MUSE will be<br />
the milestone instrument <strong>for</strong> the beginning of the next decade to study the properties of star<br />
<strong>for</strong>ming galaxies in the distant universe.<br />
References<br />
Ajiki et al. 2003, AJ, 126, 2091<br />
Barton et al. 2004, ApJ, submitted, astroph/0310514<br />
Charlot & Fall 1991, ApJ, 378, 471<br />
Charlot & Fall 1993, ApJ, 415, 580<br />
Cole et al. 2000, MNRAS, 319, 168<br />
Cowie & Hu 1998, AJ, 115, 1319<br />
Devriendt et al. 1999, A&A, 350, 103<br />
Ellis et al. 2001, ApJ, 560, 119<br />
Franx et al 1997, ApJ, 486, 75<br />
Fujita et al. 2003, AJ, 125, 13<br />
Haiman & Spaans 1999, ApJ, 518, 138<br />
Hatton et al. 2003, MNRAS, 343, 75<br />
Hu et al. 1998, ApJ, 502, 99<br />
Kennicutt 1988, ApJ, 334, 144<br />
Kudritzki et al. 2000, ApJ, 536, 19<br />
Lanzetta et al. 2002, ApJ, 570, 492<br />
Lequeux et al. 1995, A&A, 301, 18<br />
Ouchi et al. 2003, ApJ, 582, 60<br />
Partridge & Peebles, 1967, ApJ, 147, 868<br />
Rhoads et al. 2000, ApJ, 545, 85<br />
Rhoads & Malhotra 2001, ApJ, 563, 5<br />
Rhoads et al. 2003, AJ, 125, 1006<br />
Shimasaku et al. 2003, ApJ, 586, 111<br />
Silva et al. 1998, ApJ, 509, 103<br />
Steidel et al. 2001, ApJ, 546<br />
Stiavelli et al. 2001, ApJ, 561, 37<br />
Valls-Gabaud 1993, ApJ, 419, 7<br />
Venemans et al. 2002, ApJ, 569, 11<br />
Weymann et al 1998, ApJ, 505, L95
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2.3. Fluorescent emission and the cosmic web<br />
For the past three decades, analytic work (Zeldovich 1970) and cosmological simulations (e.g.<br />
White et al 1987, Evrard et al 1994, Furlanetto 2003) have been predicting that the first<br />
structures to <strong>for</strong>m in the Universe are tangled in what has been dubbed the “cosmic web”. The<br />
picture of matter collapsing into moderately overdense sheets and filaments, with galaxies and<br />
galaxy clusters <strong>for</strong>ming through continued collapse at their intersections has become common<br />
knowledge in the astronomical community. Yet, direct mapping of the cosmic web remains a<br />
challenging observational venture, especially at z ≥ 3.<br />
Several methods have been used to achieve this goal, from poking lines of sight to probe<br />
integrated one-dimensional properties (Damped Ly α system or Ly α <strong>for</strong>est studies as in e.g.<br />
Rauch 1998), to tri-dimensional surveys of galaxy populations using broad band filters<br />
(Lyman Break Galaxies e.g. Steidel et al 1999). The <strong>for</strong>mer method covers by construction a<br />
very limited portion of the sky since it relies on absorption behind an existing mesh of<br />
background quasars which are not spaced closely enough to yield in<strong>for</strong>mation on a typical<br />
filament scale. As <strong>for</strong> the latter, since it only allows one to detect the brightest of sources, it<br />
also suffers from sparse sampling of the filamentary structures.<br />
However, galaxy candidates selected<br />
<strong>for</strong> their Ly α emission using deep<br />
narrow band filters are already<br />
known to sample the high redshift<br />
galaxy population at much fainter<br />
levels than studies based on<br />
continuum emission such as LBGs<br />
(see e.g. Steidel et al 2000).<br />
T<strong>here</strong><strong>for</strong>e, one naturally expects a<br />
better sampling of the high redshift<br />
cosmic structures with such a<br />
technique. As a matter of fact, the<br />
first detection of a z = 3.04 filament<br />
by Moller & Fynbo (2001) has<br />
demonstrated the power of using<br />
Ly α emission to map the cosmic web.<br />
Moreover, mapping out filaments in<br />
their own Ly α light by finding<br />
enough star <strong>for</strong>ming knots, allows<br />
one not only to probe the small<br />
fraction of baryons embedded inside<br />
galaxies but also the more diffuse<br />
emission coming from the nearby<br />
densest portions of the Inter Galactic<br />
Medium. In fact, existing analytic<br />
Figure 2-6 : Cosmological simulations of galaxy <strong>for</strong>mation,<br />
with two phases of the baryonic gas taken into account(warm<br />
and hot phase with SPH, cold and molecular phase with<br />
sticky particles). At top is shown the dark matter particules,<br />
then the warm gas, cold gas, and the stars <strong>for</strong>med out the<br />
cold phase at bottom. From left to right are shown 4<br />
successive zooms (from Semelin & Combes 2003).
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estimates (e.g. Gould & Weinberg 1996) suggest that the surface brightness of such regions<br />
which lie within filaments but outside of galaxies, could be substantial. In other words, Ly α<br />
emission should offer a better map of the gas distribution in filaments than galaxy surveys do.<br />
Furthermore, as pointed out by Haiman & Rees (2001), diffuse Ly α -emitting gas constitutes<br />
an intrinsically interesting phase: this gas is cooling onto virialized halos, thus offering a<br />
unique opportunity to study the growth of bound objects.<br />
The technique of selecting galaxy candidates in narrow band filters which was briefly<br />
described in the previous section is costly as it involves doing ultra deep imaging and then<br />
going to large telescopes to get a spectroscopic confirmation of the redshift. This makes<br />
MUSE highly competitive since the redshifts are obtained simultaneously across the entire<br />
field. In addition, the flux limit of 1.1 × 10 -17 erg s -1 cm -2 reached by Moller & Fynbo (2001)<br />
to detect their z = 3.04 filament is well above what MUSE will reach, either in shallow or<br />
deep mode (5 × 10 -18 erg s -1 cm -2 and 3.9 × 10 -19 erg s -1 cm -2 respectively) so that one could<br />
imagine doing a shallow survey covering quite a large portion of the sky without the adaptive<br />
optics, and still gain a lot as compared to current narrow band filter surveys (as e.g. LALA) in<br />
terms of mapping the cosmic web at high redshift. As an example, it is necessary to get<br />
accurate redshifts of objects to determine their membership in groups or filaments. Such<br />
redshifts will be obtained without further overhead from such a MUSE survey. Moreover, all<br />
currently planned Ly α surveys target a redshift window 4 < z < 5 (LALA or the SUBARU<br />
survey) or z~2 (NOT survey) and none cover the range z~3 w<strong>here</strong> MUSE will have<br />
significant sensitivity. Finally, as pointed out by Weidinger at al (2002) a decent size filament<br />
survey containing a few tens of objects could also be used to meaningfully constrain the value<br />
of Ω Λ , in a way that intersects the probability curves from the various SN Ia cosmology<br />
projects. Such constraints would be coming from a modified Alcock-Paczy’nski (1979) test,<br />
involving statistical geometrical properties of filaments (lengths, radii and angles). We refer<br />
to the original work of Weidinger et al (2002) <strong>for</strong> details on this specific aspect.<br />
Finally, to illustrate the most unique point of using an instrument such as MUSE, we take<br />
advantage of the recent work of Furlanetto et al (2003) who explored the possible detection of<br />
filaments through the detection of diffuse Ly α emission at low (z = 0.15) redshift using high<br />
resolution hydrodynamical simulations. Their study is summarized in figure 2-7 which shows<br />
a surface brightness map of a large portion of the cosmic web as well as the blow up of one of<br />
its filaments. As Kunth et al (2003) rightly argue, properly computing Ly α emission from star<strong>for</strong>ming<br />
galaxies is a strenuous task, but one can nevertheless obtain simple empirical<br />
estimates. Taking those of Furlanetto et al (2003) at face value (panel (b) of figure 1), the<br />
scale on the plot is easily converted into units of erg s -1 cm -2 arcsec -2 by a simple subtraction<br />
of 21.5 from the given colour tables, so that the bottom of the colour scale on the right hand<br />
side of the figure is simply 3 × 10 -21 erg s -1 cm -2 arcsec -2 . Assuming that the filament remains<br />
unchanged at z = 3, and simply taking into account the cosmological dimming factor <strong>for</strong><br />
surface brightness which scales like (1 + z) -4 , and the shrinking of apparent diameter, one<br />
realizes that MUSE in deep field mode (whether in AO mode or not) should be able to<br />
marginally detect such diffuse Ly α emission at z = 3. (See the calculation below on<br />
fluorescence <strong>for</strong> some more detailed numbers).
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Figure 2-7: Maps of Ly α surface brightness Φ <strong>for</strong> z = 0.15 and ∆z = 10 -3 (∆λ = 1.2 Å) taken from [3]. Panel<br />
(a) assumes an angular resolution of ~ 29''; the rest show the region outlined in green with 7.2'' resolution<br />
(or ~ 13 h -1 kpc). Except <strong>for</strong> panel (a), pixels with Φ < 10 photons cm -2 s -1 sr -1 are excluded. (a), (b):<br />
Fiducial model. (c): ε α = 0 <strong>for</strong> self-shielded gas. (d): Estimated Ly-α emission from star <strong>for</strong>mation in the<br />
slice (such emission was not included in the other panels).<br />
Several authors have calculated the expected surface brightness of optically thick neutral gas<br />
illuminated by the UV background (i.e. without enhancement by a local UV source such as<br />
embedded star <strong>for</strong>mation). In figure 2-8 we show an updated version of the calculation of<br />
Gould & Weinberg (1996), using a recent estimate of the evolution of the UV background<br />
(Haardt, Private Comunication, CUBA code). As can be seen, the surface brightness of all<br />
optically thick neutral gas in the universe is close to the MUSE detection limit at z=3 if one<br />
could sum over the 10x10 arcsec characteristic radius of these optically thick clouds.<br />
Obviously the feasibility of such an observation will depend strongly on whether systematic<br />
errors begin to dominate when searching <strong>for</strong> such low signals over relatively large numbers of<br />
spatial samples.<br />
Given an estimated characteristic<br />
size <strong>for</strong> Lyman Edge absorbers,<br />
one can estimate their space<br />
density as a function of redshift.<br />
For a 50 kpc size (corresponding to<br />
approximately 10 arcsec at high<br />
redshifts), the resulting space<br />
density is roughly 3.5 x 10 -3 Mpc -3 .<br />
Combining this with the area<br />
coverage of MUSE, one can<br />
estimate that t<strong>here</strong> should be<br />
roughly 10 such systems in a<br />
MUSE field of view between<br />
3
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Preparation). This extends the results from Moller & Fynbo (2001) to z=3. The peak in PDF<br />
at higher fluxes corresponds roughly to the values calculated in Figure 2-8, supporting the<br />
idea that large areas may ‘light up’ if these surface brightnesses can be detected.<br />
References<br />
Alcock, C., & Paczy’nski, B. 1979, Nature, 281, 358<br />
Evrard, A. E., Summers, F. J., & Davis M. 1994, ApJ, 422, 11<br />
Furlanetto, S., Schaye, J., Springel, V., & Hernquist, L. 2003, ApJ, in press, astroph/0311006<br />
Gould, A., & Weinberg, D. H. 1996, ApJ, 468, 462<br />
Haiman, Z. & Rees, M. J. 2001, ApJ, 556, 87<br />
Kunth, D. et al. 2003, ApJ, in press, astro-ph/0307555<br />
Moller, P., & Fynbo, J. U. 2001, A&A, 372, L57<br />
Rauch, M. 1998, ARA&A, 36, 267<br />
Steidel, C. C. et al. 1999, ApJ, 519, 1<br />
Steidel, C. C. et al. 2000, ApJ, 532, 170<br />
Weidinger, M., M˜oller, P., Fynbo, J. U., Thomsen, B., & Egholm, M.P. 2002, A&A, 391, 13<br />
White, S. D. M., Frenk, C. S., Davis, M., & Efstathiou, G. 1987, ApJ, 313, 505<br />
Zel'dovich, Ya. B. 1970, A&A, 5, 84 3
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2.4. Reionization<br />
Because of the absence of any significant continuum absorption blueward of Ly α in the<br />
spectra of QSOs at redshifts as high as z≥5 (the so called Gunn-Peterson trough) hydrogen in<br />
the universe is highly ionized (i.e. to better than 1 part in 10000) <strong>for</strong> redshifts below 5. It is<br />
usually assumed that the hard spectra of QSOs and the softer spectra of hot stars are the prime<br />
ionizing sources at these redshifts. A similar analysis <strong>for</strong> Helium indicates that at redshifts<br />
below z≈3, Helium is also double ionized, w<strong>here</strong>as at higher redshift Helium ionization is at<br />
best only patchy. The transition in the opacity of HeII at redshift 3-4 coincides with an<br />
obvious jump in the temperature of the intergalactic medium (IGM) by a factor of ~2 (Theuns<br />
et al. 2002). This result is usually interpreted by the transition of a soft UV radiation field at<br />
z>4 that is incapable of ionizing HeII and that is dominated by stars, to a hard, HeII-ionizing<br />
UV radiation field with significant or even dominating contributions from QSOs at z6 in the SDSS followed by their<br />
spectroscopy is providing invaluable clues to the evolution of the universe at its earliest<br />
epochs. Even though QSOs at z=6.5 are far to rare to contribute significantly to the UV<br />
background, the mere presence of a luminous QSO at z=6.5, i.e. an epoch when the universe<br />
was less than 1 Gyr old, is indicative that massive structures (including supermassive black<br />
holes) must have <strong>for</strong>med at very early cosmological epochs. Within the concordance ΛCDM<br />
scenario such luminous QSOs would be hosted in halos with masses of 10 13 M sun . Even more<br />
excitingly, however, these QSO show clear indication of continuum absorption blue ward of<br />
Ly α corresponding to a neutral hydrogen fraction of ≥1% (by mass) and ≥ 0.1% (by volume),<br />
respectively. The standard interpretation is that we are witnessing the latest stages of the<br />
reionization epoch. According to numerical simulations of the propagation of ionizing<br />
photons in a ΛCDM universe (Gnedin 2000), the final stages of the reionization of the<br />
universe (the percolation phase) should happen almost instantaneously with a sharp transition<br />
from almost neutral to an almost fully ionized stage. Due to the strongly changing optical<br />
depth, a strong evolution of the abundance and the properties of so-called Ly α -emitters, the<br />
likely source of ionizing photons, is expected (see below). The red wavelength range of<br />
MUSE (probing Ly α at the redshift interval z=6-6.7) is well adapted <strong>for</strong> this crucial<br />
cosmological epoch.<br />
A second, very interesting result has been recently provided by the cosmic microwave<br />
background satellite, WMAP. Cross correlations between the temperature and polarization<br />
measurements of the CMB indicate that the total optical depth of free electrons is τ≈0.17,<br />
while a suddenly reionization at z=6.5 results in a significantly lower optical depth of τ≈0.04.<br />
However, the WMAP results are still preliminary as they are based on a cross correlation<br />
between the temperature and polarization measurements only. A detailed analysis of the<br />
polarization power spectrum is still awaiting publication. Nevertheless, should the WMAP<br />
polarization measurement be confirmed, it will highlight a very interesting inconsistency<br />
between IGM and CMB data. Un<strong>for</strong>tunately, the CMB polarization signal is only providing a
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global constraint that contributes little to the detailed time evolution of the reionization.<br />
Hydrogen must be essentially neutral over a substantial fraction of the z>6 universe, but the<br />
exact epoch is largely unconstrained. Using semi analytical and numerical models, the<br />
WMAP and QSO results can be put in concordance, if the universe experiences a very<br />
extended reionization history starting at z≈20 and ending at z≈6. However, the apparent high<br />
temperature of the IGM provides evidence that the energy associated with the reionization<br />
was invested at relatively late cosmic epochs (z6 are the ideal tests to further constrain the reionization history<br />
of the Universe because (i) they are the likely sources of ionizing UV photons and (ii) their<br />
abundance as a function of redshift directly probes the ionization state of the IGM. Even small<br />
fractions of neutral hydrogen are efficient in scattering Ly α photons in direction and<br />
frequency thus making faint emitters unobservable, unless the intrinsic line width is very large<br />
According to the simulations detailed in section 2.2 we expect 27 Ly α -emitters in a single<br />
MUSE deep field in the 6–6.7 redshift range. In the proposed survey of 5 deep fields (see<br />
section 2.12.1) we shall get 135 objects in total. By investigating their evolution, the<br />
reionization history can be probed near x HI ≈1, a regime that is poorly tested by Gunn-<br />
Peterson-trough measurements.<br />
Two main signatures that can be uniquely searched <strong>for</strong> with MUSE are the following:<br />
• If the neutral fraction falls considerably below levels of 1%, then the partly neutral<br />
IGM produces a Ly α damping wing that should absorb a significant part of the Ly α<br />
line, if the HII region produced by the galaxy around itself is not large enough to<br />
move the damping wing far away from the line center. Faint Ly α emitters should<br />
'disappear' rapidly beyond the reionization redshift (Haiman & Spaans 1999), while<br />
the brighter sources would still be visible (Cen & Haiman 2002). The luminosity<br />
function and its redshift evolution of the Ly α emitters contain in<strong>for</strong>mation on the<br />
neutral fraction and thus on reionization. Furthermore, any cosmic structure of larger<br />
than average density will induce infall of the IGM around it, i.e. the gas will “see” the<br />
source emission shifted to the blue, and absorbing red-ward of the Ly α line center; this<br />
effect may potentially wipe out most of the line. The optical depth owing to this effect<br />
increases roughly as (1+z) 4 (Haiman & Loeb 2002).<br />
• T<strong>here</strong> should be characteristic imprints from a partially neutral IGM on the Ly α line<br />
shape. This effect is hard to observe in a single source, but can be measured if one has<br />
a statistical samples of ≥ 100 Ly α emitters (argued in Haiman 2003) as provided by<br />
the MUSE deep fields.
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Figure 2-9 Left: The suppression of the total line flux relative to the unobscured line as a function of the<br />
star <strong>for</strong>mation rate of a galaxy at z=6.56. Right: The suppression of the total line flux relative to the<br />
unobscured line as a function of line width. The top lines corresponds to a model with a proper HII region<br />
size of 0.7 Mpc (f esc =1), the bottom curve describes a Ly α line model without any HII region (from<br />
Haiman 2003).<br />
The second effect is illustrated in Fig. 2-9. Prior to reionization, the line profile correlates<br />
with the size of the local HII region and t<strong>here</strong><strong>for</strong>e with the luminosity and age of the source as<br />
well as with the intrinsic line profile. For example a line as narrow as ~30 km.s -1 would<br />
essentially be erased if the star <strong>for</strong>mation rate is below 1 M sun yr -1 , but <strong>for</strong> line as broad as 300<br />
km.s -1 , 20% of the total flux would be transmitted <strong>for</strong> arbitrarily faint sources. The detailed<br />
imprints of the reionization history cannot be disentangled in narrow-band Ly α surveys that<br />
only trace the brightest objects of the population, but require a survey that probes the number<br />
function as well as the line profiles, as provided by the MUSE deep fields.<br />
At the moment, theoretical models provide little quantitative constraints on the observable<br />
significance of these effects and to what extend they are clearly observable with MUSE. For<br />
example, current model estimates of the probability of Ly α photons to penetrate the z>6 IGM<br />
range from 0.001 to ~1, a fact that demonstrates the large uncertainties involved in these<br />
estimates. The fraction of Ly α photons that manage to escape the star-<strong>for</strong>ming galaxy is<br />
likewise poorly constrained. Besides providing a detailed understanding of the reionization<br />
history of the universe, MUSE has the potential to shed light on the details of the star<br />
<strong>for</strong>mation, the IMF, and the radiation transport in this first generation of galaxies.<br />
References<br />
Theuns et al. 2002, ApJ, 567, 103<br />
Gnedin 2000, ApJ, 542, 535<br />
Haiman & Spaans 1999, ApJ, 518, 138<br />
Cen & Haiman 2002, ApJ, 570, 457<br />
Haiman & Loeb 2002, ApJ, 576, 1<br />
Haiman 2003, ApJ, 595, 1
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2.5. Feedback processes and galaxy <strong>for</strong>mation<br />
Our understanding of galaxy <strong>for</strong>mation is making rapid advances. Improvements in our<br />
knowledge of the basic cosmological parameters (Ω 0 , H 0 , Γ 0 , etc., Bennett et al., 2003), and<br />
developments in computer simulation techniques mean that we are able to accurately trace the<br />
collapse of dark matter structure (eg., Jenkins et al. 2001). The outstanding difficulty is now<br />
to understand how the baryonic component collapses down to <strong>for</strong>m galaxies. Computer<br />
simulations that incorporate gas cooling lead to the <strong>for</strong>mation of far too many small galaxies<br />
in the early universe. While they predict that more than 50% of baryons are able to cool and<br />
<strong>for</strong>m into stars, the observed fraction is only 8%! This problem is often referred to as the<br />
cosmic cooling crisis (White & Rees, 1978, Cen & Ostriker, 1993, Balogh et al., 2001) and is<br />
closely related to the angular momentum problem that causes model galaxies to be too small<br />
(Navarro & Steinmetz, 1997).<br />
The reason <strong>for</strong> this crisis is that these simulations lack effective feedback. Clearly it is not<br />
enough to simply let the gas cool, the<br />
rate of cooling must be balanced by the<br />
injection of energy from SNe or AGN.<br />
But while the idea is widely accepted,<br />
the actual mechanism is poorly<br />
understood, and even more poorly<br />
constrained by observations. One of<br />
the most popular explanations is superwinds:<br />
high power blast-waves that<br />
sweep nascent galaxies clean of their<br />
interstellar medium, driving it to<br />
distances of 0.5 - co-moving Mpc, so<br />
that the ejected gas is never able to<br />
collapse back onto the proto-galaxy<br />
(Springel & Hernquist, 2003, Benson<br />
et al.2003). The idea is appealing<br />
because it would also explain the<br />
wide-spread distribution of metals<br />
through-out the universe (Theuns et<br />
al., 2002) and may resolve the spiral<br />
disk angular momentum problem too.<br />
However, observational support <strong>for</strong><br />
superwinds is tantalising but elusive.<br />
Local analogues <strong>for</strong> high power<br />
superwinds may exist in dwarf star<br />
burst galaxies (such as M82, Martin<br />
1999). In these galaxies, a powerful<br />
star burst drives some of ISM out of<br />
the galaxy at speeds of up to 600 km/s.<br />
However (1) these galaxies are dwarfs<br />
Fig 2-10: The velocity structure of the Ly α halo “blob1” in<br />
SSA22 from observations with SAURON on the WHT (Bower et<br />
al., 2003). The image is colour coded to show Ly α emission<br />
that is red and blue shifted compared to the sub-mm source. In<br />
addition to the complex dynamics of the halo of the submm<br />
source, the two lyman break galaxies in the field also have<br />
distinct emission line haloes. This is most clearly seen <strong>for</strong> the<br />
C15 source. This halo has a velocity shear across it that<br />
suggest the ionised gas is being expelled in a bipolar outflow.<br />
The flow is similar to local star burst galaxies except that it is<br />
much more luminous.
- it is unclear that the gas<br />
would escape from a larger<br />
galaxy, (2) little mass is<br />
involved in this wind,<br />
insufficient to explain the<br />
cosmic cooling crisis.<br />
At high redshift, superwinds<br />
may be more widespread and<br />
even more powerful. Evidence<br />
<strong>for</strong> high-z superwinds comes<br />
from comparing the redshifts<br />
of galaxies measured from Ly α ,<br />
nebular lines (in the observed<br />
IR) and ISM absorption lines.<br />
These redshifts are often<br />
discrepant at the level of 300<br />
km/s, which Pettini et al.<br />
(1998; Shapley et al 2001, Fig.<br />
1.8) interpret as a P-cygni<br />
effect in the super-wind<br />
outflow. It is not clear,<br />
however, whether this wind<br />
will actually escape the galaxy<br />
(or fall back in a galactic<br />
fountain), nor whether the wind<br />
includes substantial fraction of<br />
the galaxy's baryonic mass. To<br />
answer these questions we<br />
need to look at how far from<br />
the galaxy the wind extends.<br />
We would like to see if the<br />
super-winds create hot<br />
outflowing bubbles around the<br />
proto-galaxies.<br />
Title: Science Case<br />
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The SAURON deep field<br />
In preparation <strong>for</strong> the deep surveys planned <strong>for</strong> MUSE, a pilot<br />
programme has been developed using the SAURON IFU<br />
spectrograph (Bacon et al. 2001). We have now surveyed<br />
three fields, with a paper (Bower et al, MNRAS) describing<br />
the first of these now in press. We have studied the structure<br />
of the Ly α emission-line halo, LAB1, surrounding the submillimetre<br />
galaxy SMM J221726+0013. The field (41×33<br />
arcsec² sampled at 0.95 arcsec) was observed <strong>for</strong> a total of 9<br />
hours split in 30 mn exposures. The measured limiting<br />
surface brightness is found to be from 1×10 −18 erg s −1 cm −2<br />
per sq. arcsec <strong>for</strong> lines with σ = 2Å to 3.5×10 −18 erg s −1 cm −2<br />
per sq. arcsec <strong>for</strong> lines with σ = 20Å. The observations trace<br />
the emission halo out to almost 100 kpc from the submillimetre<br />
source and identify two distinct Ly α “mini-haloes”<br />
around the nearby Lyman-break galaxies. The main emission<br />
region has a broad line profile, with variations in the line<br />
profile seeming chaotic and lacking evidence <strong>for</strong> a co<strong>here</strong>nt<br />
velocity structure. Around the Lyman-break galaxy C15, the<br />
emission line is narrower, and a clear shear in the emission<br />
wavelength is seen. A plausible explanation <strong>for</strong> the line<br />
profile is that the emission gas is expelled from C15 in a<br />
bipolar outflow, similar to that seem in M82.<br />
The second field is centered on a bright QSO (HB89-<br />
1738+350). This is a V=20.5, z=3.239 QSO chosen so that its<br />
rest frame Ly α would be inside the small SAURON spectral<br />
range, but also so that the cube would include a significant<br />
range w<strong>here</strong> intervening absorption systems seen along the<br />
line of sight to the QSO could be correlated with any<br />
emission line objects found in the SAURON cube. More<br />
recently an even deeper exposure of 20 hours on the second<br />
Ly α peak in SSA22 has been obtained. Analysis is in<br />
progress.<br />
Although SAURON was not optimized <strong>for</strong> this type of<br />
science, it demonstrates the capabilities of IFU <strong>for</strong> deep<br />
fields.<br />
The MUSE instrument will play a crucial role in determining the nature of feedback in high<br />
redshift galaxies; and thus solving one of the most pressing problems in extra-galactic<br />
astronomy.<br />
2.5.1. Understanding Feedback with Spatially Resolved Galaxies<br />
With the high spatial sampling, sources brighter than 3.9 10 -18 erg.cm -2 .s -1 will have Ly α<br />
emission that can be spatially resolved. T<strong>here</strong> will be ~60 such sources in each 80 hour<br />
pointing. In the local star burst galaxies, the material being ejected from the galaxy is seen as<br />
a bipolar outflow. Our observations of the diffuse halo of Lyman break galaxy C15 in the
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SSA22 proto-cluster (z=3.09) hint that the same is likely to be true in high redshift systems<br />
(Fig 2-10).<br />
The geometry of this flow is an important constraint. Is the galaxy <strong>for</strong>mation process<br />
terminated by an explosion that drives a near spherical shell, or is t<strong>here</strong> a balance between a<br />
bi-polar outflow and continued inflow along orthogonal directions? These are key questions<br />
that we can compare to numerical simulations that are being developed to model super-wind<br />
out-flows in proto-galaxies.<br />
Each pointing will identify ~15 objects with continuum magnitudes brighter than I AB =23, we<br />
will detect the rest-frame UV continuum with sufficient s/n to map the velocity structure of<br />
the neutral ISM through absorption lines such as SiII. This will allow us to map the structure<br />
of both the emitting and absorbing material, making a very detailed test of the geometry of the<br />
outflow/inflow and thus allowing us to assess the balance of cooling and feedback.<br />
2.5.2. Measuring Feedback with QSO sightlines<br />
A powerful technique <strong>for</strong> studying the larger scale impact of feedback is to target fields<br />
containing QSOs that are sufficiently bright <strong>for</strong> absorption line studies. In this way, the<br />
redshifts of the Ly α emitters can be compared to absorption features in the QSO spectrum<br />
(often referred to as the Ly α <strong>for</strong>est), allowing us to probe the association between the young<br />
galaxies and the neutral gas from which they <strong>for</strong>m.<br />
Adelberger et al., (2003) per<strong>for</strong>med this experiment using Lyman-break galaxies at z~3.<br />
For galaxies with a large separation (>2 co-moving Mpc) from the QSO sight-line, they found<br />
that t<strong>here</strong> was a higher than average probability of an absorption feature, as is shown in<br />
Figure 2-11. This is the result of the cosmic web discussed in section 2.3 and shows that<br />
galaxies are <strong>for</strong>med in regions of large scale overdensity, as we would expect from<br />
simulations of the large-scale structure of the universe.<br />
At small separations (
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In a single MUSE field, we expect to detect 100 emitters over the redshift range 2.8 to 4 in a<br />
10 hour exposure. The typical sizes of the virial halos associated with these galaxies, as<br />
derived from the simulations, are 0.2 Mpc radius, only a factor 1.8 smaller than the Lymanbreak<br />
galaxies selected by Adelberger et al. Among these 100 galaxies, we expect to find 26<br />
objects bright enough to have spatially resolved in<strong>for</strong>mation. T<strong>here</strong> are 59 currently known<br />
QSOs at z>4 that are sufficiently bright (V>100, or 1% accuracy in absorption) can be obtained from the data cube. An optimal subsample<br />
can be selected from these quasars to ensure that the sight line is not blocked (at<br />
z>2.8) by a damped absorption line system. Re-observing the quasar with an echelle<br />
spectrograph like UVES would allow the absorption features to be deblended and centroided<br />
individually, but this is not strictly required since we will need only to determine the mean<br />
transmission at the systemic redshift of the proto-galaxy. A more significant issue is the offset<br />
between the systemic redshift and that measured from Lyman alpha emission, but Adelberger<br />
convincingly demonstrates that this can be determined by cross-correlating the absorption line<br />
data.<br />
If we targeting 4 such fields, we<br />
will obtain a sample of 400 objects,<br />
including 100 spatially resolved. In<br />
contrast Adelberger et al.'s results<br />
are based on only 6 objects. Thus,<br />
rather than simply detecting the<br />
neutral hydrogen deficit, the size of<br />
the MUSE sample will allow us to<br />
measure the strength of the superwind<br />
as a function of galaxies'<br />
emission line strength and<br />
continuum flux (both measures of<br />
the star <strong>for</strong>mation rate). We would<br />
be able to divide the sample into a<br />
6x6 grid of luminosity and<br />
separation from the QSO sightline,<br />
and to still measure the average<br />
neutral hydrogen density in each<br />
bin to better than 5%. This sample<br />
will revolutionise our view of<br />
feedback, allowing us to study the<br />
strength, geometry and impact of<br />
the superwind as a function of the<br />
underlying star <strong>for</strong>mation rate and<br />
galaxy mass. We have seen how<br />
the large galaxies samples<br />
available from the SLOAN survey<br />
have revolutionarised our view of<br />
the local universe. The size of the<br />
sample we derive from MUSE will<br />
similarly revolutionise our view of<br />
Fig 2-11. The mean transmission at the redshift of the protogalaxy<br />
as a function of the distance of the proto-galaxy from the<br />
line of sight, from Adelberger et al., (2003). The mean<br />
transmission at randomly chosen redshifts is shown as a<br />
horizontal dashed line. As the separation between the protogalaxy<br />
and the line of sight decreases, the transmission initially<br />
drops. This is due to the large-scale association of proto-galaxies<br />
and Ly α absorbers. This trend is expected from theory (as shown<br />
by the thin dotted and dashed lines). At small separations,<br />
however, the trend is reversed and the transmission increases. At<br />
separations
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the feedback in the high redshift universe. Although we will initiate this programme with the<br />
VIMOS spectrograph, only the throughput and greater field of view of MUSE will allow us to<br />
build the large and comprehensive database required. The equivalent programme would take<br />
40 times longer to complete with VIMOS due to MUSE's greater sensitivity and larger field<br />
of view (the programme cannot use the low dispersion mode of VIMOS). Only the higher<br />
spatial sampling of MUSE will allow us to spatially resolve the emission from the protogalaxies.<br />
In longer integrations we can identify much more distant emission-line galaxies. We will<br />
target QSOs at higher redshifts in order to determine how the strength and effectiveness of the<br />
super-wind feedback evolves with redshift. At present only three SLOAN QSOs (V30), but we will still<br />
be able to determine the mean absorption to better than 10% at the redshift of each emissionline<br />
object. In a single 80 hour exposure, we expected to detect almost 300 emission line<br />
objects which can be used <strong>for</strong> this study. 200 of these would lie at z>4, giving us an<br />
unparalleled insight into the role of feedback in the <strong>for</strong>mation of the first galaxies and the<br />
widespread pollution of the universe with the first metals.<br />
References<br />
Adelberger, K.L., Steidel C.C., Shapley A.E., Pettini M., 2003, astro-ph/0210314<br />
Balogh M., Pierce F., Bower R.G. & Kay S., 2001, MNRAS, 326, 1228<br />
Benson A., Bower R.G. et al., 2003, ApJ, astro-ph/0302450<br />
Bower R.G., Morris S., Bacon R. et al. 2003, MNRAS, in press<br />
Cen R. & Ostriker J., 1993, ApJ, 417, 404<br />
Martin C., 1999, ApJ, 513, 156<br />
Navarro & Steinmetz 1997, ApJ, 478, 13<br />
Pettini M., Kellog E., Steidel C.C., et al., 1998, 508, 539<br />
Springel V. & Hernquist L., 2003, MNRAS, 339, 289<br />
Shapley A. E., Steidel C. C., Adelberger K.L., et al., 2001, ApJ, 562, 95<br />
Theuns T., Viel M., Kay S., et al., 2002, ApJ, 578, L5.<br />
White S. D.M., Rees M.J., 1978, MNRAS, 183, 341
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2.6. Ultra-deep survey using strong gravitational lensing<br />
The field size of MUSE is very well matched to those of strongly lensing clusters, which have<br />
typical Einstein radii of 15-30 arcsec, to a maximum of 45 arcsec <strong>for</strong> Abell 1689. The strong<br />
lensing of these clusters allows a number of unique studies, which are outlined below.<br />
2.6.1. Exploration of the luminosity function to much fainter limits<br />
The sizes of objects at our detection limit of 3.9<br />
10 -19 erg.s -1 .cm -2 are expected to be small, and<br />
the objects are essentially unresolved. Hence<br />
the S/N will be amplified by the magnification<br />
factor, which is between 3 and 5 over the whole<br />
field. Hence we can probe the luminosity<br />
function 3 times deeper, <strong>for</strong> an area which is 3<br />
times smaller than the typical deep field. We<br />
show a simulation in Figure 2-13. The lensing<br />
cluster has an Einstein radius of 30 arcsec, and<br />
the source distribution is taken from a GALICS<br />
simulation. Only the brightest Ly α emitters are<br />
shown in the image, w<strong>here</strong> color indicates<br />
redshift. It is obvious that t<strong>here</strong> are many<br />
multiply imaged galaxies, and many systems<br />
with large magnification. In total, over 200<br />
lensed objects are detected to our flux limit.<br />
The power of this technique was demonstrated<br />
by the discovery of a lensed Ly α emitter at<br />
z=6.56 by Hu et al (2002). This faint emitter has<br />
an apparent flux of 2.7 10 -17 erg.s -1 .cm -2 , and is<br />
lensed by a factor of ~4.5. Hence it would be<br />
undetectable without the lensing (which speeds<br />
up the integration time by a factor of 20 !). Ellis<br />
et al used lensing to find an even weaker source<br />
at z=5.6, with an unlensed flux of<br />
~3.10 -18 erg.s -1 .cm -2 , and a magnification of a<br />
factor of 30. Obviously, such strong lensing<br />
occurs only <strong>for</strong> a small area in the source plane<br />
and would not apply to most of the sources<br />
detected by MUSE, most of which are lensed by<br />
a factor between 2 - 5.<br />
Figure 2-12: An HST-ACS image of the lensing<br />
cluster Abell 1689 (Broadhurst et al, in<br />
preparation). This cluster is a prime candidate<br />
<strong>for</strong> strong lensing studies, given its very large<br />
Einstein radius, and the large number of arcs<br />
identified. Broadhurst et al identified at least 7<br />
systems which were multiply imaged. The upper<br />
panel shows the full image, the lower panels show<br />
some of the strongly lensed galaxies
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2.6.2. Constraints on the dark matter distribution and cosmology<br />
We expect roughly 10-30 multiply imaged sources in the datacube, in a wide range of<br />
redshifts. Since we know the redshifts of all sources, it is trivial to find the counter images,<br />
and unprecedented maps can be made of the mass distribution. The strength of the lensing<br />
signal as a function of source redshift depends on cosmology and the radial mass profile. If a<br />
sufficient number of multiply imaged sources are found, then the sources can be grouped into<br />
bins at the same radius and the cosmology dependence can be measured to great accuracy.<br />
2.6.3. Detailed studies of "large" arcs<br />
The Adaptive Optics capability of MUSE will allow, <strong>for</strong> the first time, to obtain very high<br />
resolution IFU spectroscopy of arcs in the optical. The simulation shows that 5-10 arcs with<br />
strong magnification can be observed per cluster. The MUSE observations will provide<br />
exquisite signal-to-noise and detail <strong>for</strong> these arcs. The AO-assisted spatial resolution of<br />
MUSE produces a gain of a factor of 3–4 in resolution compared to what other instruments<br />
can deliver in median seeing. The additional gain of the lensing is usually on the order of 5<br />
to 10 in the tangential direction, and 1–2 in the radial direction. The value of using arcs <strong>for</strong><br />
high resolution studies has been demonstrated already. We show two examples in Figures 2-<br />
14 and 2-15. Figure 2-15 shows the spectrum of the arc at z=4.92 in the cluster MS1358+62<br />
(Franx et al 1997). This arc, the highest redshift arc known at this moment, shows clear<br />
velocity structure both in the very strong Ly α emission and interstellar absorption lines like Si<br />
II 1260 Å. The velocity offset<br />
between the lines was the first<br />
evidence <strong>for</strong> large-scale winds in<br />
high redshift galaxies.<br />
Another example in shown in Fig<br />
2-14, which shows a lensed z=1<br />
galaxy in the field of the cluster<br />
Abell 2218, observed by<br />
Swinbank et al (2003). The<br />
authors were able to reconstruct<br />
the 2D velocity field from the<br />
magnified O [II] 3727 Å<br />
emission-line field, and were<br />
able to derive an inclination<br />
corrected circular velocity which<br />
agrees well with the value<br />
expected from the (local) Tully-<br />
Fisher relation. MUSE will be<br />
able to extend this work to much<br />
smaller galaxies, and to<br />
continuum studies of high<br />
redshift galaxies. It will provide<br />
unique insight into the nature of<br />
high redshift galaxies which can<br />
otherwise only obtained by 30-m<br />
or larger telescopes.<br />
Figure 2-13: A simulation of an 80 hour MUSE observation of<br />
lensed Ly α emitters behind a cluster with an Einstein radius of 30<br />
arcsec. The original distribution of emitters was taken from the<br />
GALICS simulation. The color indicates redshift, with the reddest<br />
color at the highest redshift. As can be seen, many arcs are visible,<br />
with magnifications larger than 5. Furthermore, many multiply<br />
imaged sources can be identified, and sources well away from the<br />
Einstein radius are still significantly magnified.
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Figure 2-14: The structure of the z=1 lensed galaxy in the cluster Abell 2218. The left panel shows the<br />
HST image, the middle panel shows the flux distribution of the OII emission observed with GEMINI, with<br />
the observed velocity field superimposed. The right panel shows the velocity field after "de-lensing". It is<br />
very regular, and the derived rotational velocity agrees well with the Tully-Fisher relation. MUSE will<br />
allow these studies <strong>for</strong> arcs with much smaller sizes, lensed z=3 galaxies, etc.<br />
Figure 2-15: left: a long slit spectrum of the arc at z=4.92 in the cluster CL1358+62. The Ly α emission, and<br />
several interstellar absorption lines are clearly visible. These lines show structure along the arc, in flux and<br />
velocity. Right: the velocities of Ly α and Si II 1260 Å in the arc. Both lines show similar velocity structure,<br />
and a systematic offset between them. This structure is evidence <strong>for</strong> winds, w<strong>here</strong> the neutral medium<br />
producing the Si II absorption line absorbs or scatters the Ly α emission at the same velocity.<br />
We plan to obtain 2 deep exposures with MUSE on a lensing cluster; but it is clear that<br />
MUSE will be the ideal instrument <strong>for</strong> the community to follow up lensing clusters. A prime<br />
candidate is Abell 1689, <strong>for</strong> which the HST-ACS image showed an unprecedented number of<br />
arcs (figure 2-13). We notice that lensing clusters are employed <strong>for</strong> deep searches in many<br />
wavelength bands, from sub-mm to optical, as they provide the unique opportunity to dig well<br />
below the standard sensitivity limits. MUSE will be the ideal follow-up instrument <strong>for</strong> most<br />
of these searches.<br />
References<br />
Ellis, R., Santos, R., Kneib, J.-P., Kuijken, K., ApJ 560, L119<br />
Franx, M., et al, 1997, ApJ 486, L75<br />
Hu et al, 2002, ApJ 568, L75<br />
Swinbank, A. M., et al, 2003, astro/ph 0307521
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2.7. Resolved spectroscopy at intermediate redshift<br />
The sensitivity and high resolution capabilities of<br />
MUSE will enable us to measure spatially resolved<br />
properties of galaxies at intermediate redshifts, z
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an emission line surface brightness through a Schmidt star-<strong>for</strong>mation law, normalised to a<br />
total flux of 10 -17 erg s -1 cm -2 . Consistent with Fig 1, the velocity field can be mapped with<br />
MUSE to approximately two disk scale lengths. Clearly, in addition to the rotation curves <strong>for</strong>,<br />
e.g., Tully-Fisher studies as a function of internal galactic properties, any internal kinematic<br />
sub-structure on these scales will also be detected by MUSE, allowing <strong>for</strong> example the<br />
investigation of environment-induced perturbations to the velocity fields, and their possible<br />
effect on global galactic properties such as total galactic star <strong>for</strong>mation rates and metal<br />
enrichment properties.<br />
For all galaxies with 0.25 10 -17 erg s -1<br />
cm -2 and R,I AB < 22.5. Note that this simple calculation does not take<br />
into account the beneficial effects of spatial inhomogeneities such as<br />
spiral structure in tracing the emission further out, nor does it take into<br />
account averaging over adjacent spaxels further out in the galaxy<br />
profile.
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study the radial gradients in a symmetric galaxy. The central panels of Figure 2-18 then<br />
show the resulting simulated S/N=15 spectra that are obtainable at redshift z=1, in a 80h<br />
MUSE DF integration. The spectra are obtained by combining simple stellar populations<br />
SEDs using the Bruzual & Charlot (2003) models. Finally, the right-most panels of Figure 2-<br />
18 show, <strong>for</strong> the two stellar populations, the 99% confidence levels <strong>for</strong> the recovered star<br />
<strong>for</strong>mation histories in terms of average stellar ages and metallicities, with superimposed the<br />
correct average input values (red/blue stars). The epoch of the local star <strong>for</strong>mation episode<br />
and the average metallicity of the stellar populations are both superbly recovered from the<br />
simulated MUSE data. These impressive capabilities of MUSE in probing the spatiallyresolved<br />
star <strong>for</strong>mation histories of galaxies at intermediate redshifts will allow <strong>for</strong><br />
quantitative tests of competing scenarios by discriminating between inside-out and outside-in<br />
<strong>for</strong>mation and assembly of stellar mass in massive galaxies.<br />
Fig 2-18: Stellar population analysis achievable in a 80h MUSE integration at a galactocentric distance as<br />
given in Fig. 1 (but summing over a 9 pixels annulus) . Top and bottom panels describe two different star<br />
<strong>for</strong>mation histories. Left: Modelled star-<strong>for</strong>mation rates (solid lines) and calculated metallicities (dashed<br />
lines). Center: Corresponding simulated MUSE 15σ spectra. Right: Average stellar ages and metallicities<br />
recovered from the MUSE spectra (compared with input values, represented by the red/blue star).<br />
The number density of galaxies in the field with I AB 10 -17 erg s -1 cm -2 is of order<br />
6 per arcmin -2 and 2–3 arcmin -2 , respectively. Thus, the analysis of the several MUSE deep<br />
fields will already provide a useful sample of galaxies at those crucial intermediate epochs to<br />
be studied in full detail. Summing over a few adjacent spaxels inside galaxies will allow<br />
significantly fainter flux and surface brightness levels to be reached, while still disentangling
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radial variations in gaseous and stellar properties inside galaxies. A moderate binning over<br />
about 10 spaxels will about triple the number of galaxies per MUSE field <strong>for</strong> which spatiallyresolved<br />
spectroscopic in<strong>for</strong>mation <strong>for</strong> the emitting gas is obtainable. The wider Medium<br />
Deep Field will also allow us to per<strong>for</strong>m resolved spectroscopy of galaxies at intermediate<br />
redshifts. The three-fold higher limiting fluxes will reduce the number density of galaxies on<br />
which detailed data can be obtained by a factor of about three with respect to the Deep field,<br />
but this will be more than compensated by the factor of about ten larger area. The median<br />
redshift will be reduced by about 40%; however, it will still be in the realm w<strong>here</strong> significant<br />
evolutionary changes are observed in the galaxy population. Unprecedented, the MUSE deep<br />
and medium deep fields will thus provide a sample of field galaxies in the z~0.5–1 redshift<br />
regime that will allow the investigation of the internal galactic properties as a function of<br />
fundamental global galactic properties such as mass and bulge-to-disk ratio.<br />
In addition to the observations of lensing clusters, which may be at relatively low redshift,<br />
studies of resolved galaxies in higher redshift galaxy clusters will certainly be developed by<br />
the scientific community. In such galaxy clusters at z ~ 0.8, the number density of galaxies<br />
with emission properties adequate <strong>for</strong> a spatially resolved study with MUSE is even higher<br />
than in the field. Using the K-band luminosity function of Ellis & Jones (2003), the typical I-<br />
K colors of cluster galaxies (Stan<strong>for</strong>d et al. 2002), about 10–15 galaxies can be studied at the<br />
above levels with a single MUSE pointing in a rich cluster at z~0.8. At these intermediate<br />
epochs, theory and simulations predict major galactic trans<strong>for</strong>mations in clusters driven by<br />
environmental processes such as harassment and tidal stripping. The comparison of the<br />
spatially resolved stellar and gaseous diagnostics between intermediate-z galaxies in clusters<br />
and in the field will quantify the properties and timescales, and elucidate the physics, of such<br />
trans<strong>for</strong>mations.<br />
The study of the spatially resolved properties of normal galaxies will complement the<br />
exquisite study of a small number of highly-lensed objects behind clusters (section 2.6).<br />
Reference<br />
Bruzual, G. & Charlot, S., 2003, MNRAS, 344, 1000<br />
Carollo, C.M., Lilly, S., 2001, ApJL, 548, 153<br />
Chabrier 2003, PASP, astro-ph/0304382<br />
Ferreras, I. & Silk, J., 2003, MNRAS, 344, 455<br />
Lilly, S., Carollo, C.M., Stockton, A., 2003, ApJ 597, 730.<br />
Pagel, B., et al. 1979, MNRAS, 189, 95<br />
Stan<strong>for</strong>d, S., et al, 2002, ApJS 142, 153<br />
van Zee, et al., 1998, AJ 116, 2805.
Title: Science Case<br />
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2.8. Sunyaev-Zeldovich effect<br />
In the near future, systematic surveys <strong>for</strong><br />
Sunyaev-Zeldovich (SZ) sources by<br />
bolometer arrays (e.g. BOLOCAM),<br />
interferometers and Planck and will produce<br />
large catalogues of clusters. Because the SZ<br />
effect is independent of distance, the<br />
selection is independent of redshift <strong>for</strong> a<br />
given mass and the redshift distribution is<br />
given by the cosmological volume element<br />
and the comoving density of clusters of the<br />
appropriate mass. <strong>for</strong> the concordance<br />
cosmology, BOLOCAM's dN/dz peaks at a<br />
redshift of z ~ 0.6 and falls by about a factor<br />
of 30 at z ~ 2. That of Planck peaks at even<br />
lower redshift z ~ 0.2 and falls by a factor of<br />
30 at z ~ 0.8 (Benson et al 2002).<br />
It is not possible to measure the redshifts of<br />
the density enhancements producing the SZ<br />
signal from the SZ effect itself. However,<br />
measuring the redshift distribution of the<br />
clusters would enable determination of<br />
important cosmological parameters. In<br />
addition to determinations of cosmological<br />
model Ω i which are independent from those<br />
derived from the CMB fluctuations, the<br />
accurately determined redshift distribution is<br />
sensitive to both the power spectrum<br />
normalisation, σ 8 , and the gaussianity of the<br />
primordial fluctuations (G) (see Benson et al<br />
2002).<br />
BOLOCAM has a beam of 1 arcminute<br />
which is perfectly matched to the FOV of<br />
MUSE. Planck's FWHM ~ 8 arcmin beam<br />
should still allow localisation of the<br />
gravitational potential within the MUSE<br />
FOV. At early epochs, it can no longer be<br />
assumed that cluster members can be<br />
identified from a tight "red sequence" of<br />
passively evolving elliptical-like galaxies.<br />
The unique capability of MUSE to<br />
determine redshifts <strong>for</strong> all galaxies within<br />
the FOV will make it the instrument of<br />
Fig 2-19. Redshift distribution of SZ sources from<br />
BOLOCAM and Planck (from Benson et al 2002)<br />
Fig 2-20: Variations in the N(z) <strong>for</strong> BOLOCAM SZ<br />
samples with gaussianity G (left) and σ 8 (right).
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choice to follow-up the most distant, and most interesting, SZ clusters, since the strongest<br />
peak in the redshift distribution will presumably be the redshift of the cluster.<br />
In fact, since these SZ-selected clusters are likely to be the most distant clusters selected only<br />
according to their mass (as opposed to hosting a powerful quasar or other atypical signpost),<br />
MUSE will be an ideal instrument to study the early evolution of rich environments which<br />
will evolve into the most massive clusters today. The physical size of the FOV (of order 500<br />
kpc at z ~ 2) is perfectly matched to the core radius of present-day clusters such as Coma.<br />
References<br />
Benson et al 2002, MNRAS 331, 71<br />
2.9. Late <strong>for</strong>ming population III objects<br />
The transition between Pop III and Pop II (characterised by different star-<strong>for</strong>mation processes,<br />
especially in the realm of cooling) is thought to occur at Z ~ 10 -4 Z sun . It is likely that the<br />
global enrichment of the Universe went through this transition at redshifts much higher than<br />
can be probed with MUSE (z ~ 15, or higher). Pop III objects may nevertheless be found<br />
<strong>for</strong>ming at much lower redshifts, well within the MUSE-accessible range, if the metal<br />
enrichment from the earlier objects was not widely distributed through the IGM (see e.g.<br />
Scanapieco et al 2003), i.e. leaving<br />
essentially pristine regions in the voids.<br />
The fraction of Lyman α emitters that<br />
will be Pop III objects as a function of<br />
redshift is heavily dependent on the<br />
distribution of metals and fairly<br />
independent of the mean metallicity of<br />
the Universe or the precise value of the<br />
transition metallicity (Scanapieco et al<br />
2003). The luminosities of such objects<br />
depend on the poorly understood physics<br />
of young systems, such as the initial<br />
mass function.<br />
Recent studies with existing or new<br />
stellar tracks have predicted the<br />
properties of low metallicity and PopIII<br />
starbursts (Tumlinson et al 2001, 2003,<br />
Schaerer 2002, 2003). Interestingly it<br />
appears that proto-galaxies containing<br />
essentially PopIII stars could be easily<br />
distinguished from classical galaxies,<br />
due to the harder ionizing spectrum<br />
expected from metal-free stars, which<br />
strongly enhances the strength of He II<br />
recombination lines.<br />
Fig. 2-21 Predicted restframe EUV-optical spectrum<br />
of a young Population III galaxy with a Salpeter IMF<br />
from 1-500 Msun. The dashed line shows the pure<br />
stellar emission - the solid line the total emission.<br />
(Schaerer 2002)
Title: Science Case<br />
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The following three features can be identified as clear signatures of very metal-poor or PopIII<br />
starbursts (primeval galaxies):<br />
• A larger Lyman continuum flux,<br />
and a continuum dominated by<br />
nebular emission, leading to a<br />
flatter intrinsic SED compared to<br />
normal galaxies.<br />
• For young bursts the maximum<br />
Ly α equivalent width increases<br />
strongly with decreasing<br />
metallicity from W(Ly α ) ~ 250-350<br />
Å at Z >~ 1/50 Z sun to 400-850 Å<br />
or higher at Z between 10 -5 and 0<br />
(Pop III) <strong>for</strong> the same Salpeter<br />
IMF. This is illustrated in Fig. 2-22<br />
considering also various IMF at<br />
low metallicity.<br />
• Strong HeII recombination lines<br />
(1640, 4686 Å) are a quite unique<br />
signature due to hot massive main<br />
sequence stars of PopIII/very low<br />
metallicity. Significant HeII<br />
emission is, however, only<br />
expected at metallicities below 10 -5<br />
solar (figure 2-21).<br />
Figure 2-22: Predicted Ly α equivalent widths <strong>for</strong> bursts of<br />
different metallicities and IMFs (from Schaerer 2003).<br />
The squares are <strong>for</strong> IMF 50-500Mo, the triangles 1-<br />
500Mo, and the circles 1-100 Mo. The various curves<br />
correspond to increasing metallicity from top to bottom.<br />
The second characteristic could also be<br />
found in AGNs, but enough spectral<br />
resolution (R>1000) will allow to<br />
distinguish between the two possibilities.<br />
With the help of the Table 4 from Schaerer<br />
(2003), the Ly α line emission can be<br />
estimated, <strong>for</strong> a constant star <strong>for</strong>mation of<br />
SFR= 2 M sun .yr -1 , and a photon escape<br />
fraction of 0.5, with an assumed<br />
metallicity of 10 -3 solar (and a non<br />
extreme, intermediate, IMF), to be 4 10 42<br />
erg.s -1 , corresponding <strong>for</strong> a proto-galaxy at<br />
z=7, to the line flux of about 2 10 -17<br />
erg.s -1 .cm -2 .<br />
For the HeII 1640 line, the line luminosity<br />
in the same conditions is 10 39 erg/s, and<br />
will give a flux of about 10 -20 erg.s -1 .cm -2 ,<br />
<strong>for</strong> a redshift z=5. This last line will be too<br />
faint to be detectable. However, at even<br />
Figure 2-23 : Predicted hardness as a function of<br />
metallicity <strong>for</strong> starbursts between PopIII and normal<br />
metallicities (from Schaerer 2003). The 3 curves are <strong>for</strong><br />
the 3 different IMF indicated (Mup= 100 or 500Mo,<br />
Mlo=1 or 50Mo)
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lower metallicities, <strong>for</strong> truly primordial objects, the HeII 1640 line is favoured relative to Ly α<br />
(see Figure 2-21); <strong>for</strong> some assumed IMF, the HeII 1640 line luminosity could reach 4.10 41<br />
erg.s -1 at zero metallicity, corresponding to a flux of 3.10 -18 erg.s -1 .cm -2 , at z=5. Such a line<br />
would be easily detectable in the MUSE deep field. Finally, the MUSE ultra deep field<br />
described in section 6 (using gravitational amplification by a factor 3 in average), with its<br />
enhanced detection limit of 8.10 -20 erg.s -1 .cm -2 , should be able to detect simultaneously Ly α<br />
and HeII lines in the 2.8-4.7 redshift range <strong>for</strong> a metallicity lower than 10 -5 solar.<br />
Based on the models of Scanapieco et al (2003), the fraction of Ly α emitters that are Pop III<br />
objects could under certain scenarios be as high as 10% at z ~ 5 and L Lyα ~ 10 43 erg s -1 cm -2 .<br />
The point is that this is highly model dependent, and the detection of such objects (which is<br />
quite plausible) would greatly add to our understanding of the early chemical enrichment of<br />
the Universe.<br />
References<br />
Scanapieco, E., Schneider, R., Ferrara, A., astro-ph/0301628.<br />
Schaerer, D., 2002, A&A, 382, 28<br />
Schaerer, D., 2003, A&A, 397, 527<br />
Tumlinson, J., Giroux, M.L., Shull, J.M., 2001, ApJ, 550, L1<br />
Tumlinson, J., Shull, J. M., Venkatesan, A.: 2003, ApJ, 584, 608<br />
2.10. Active galactic nuclei at intermediate and high redshifts<br />
In a dramatic change of paradigm over the last years, active galactic nuclei (AGN) have<br />
altered their status from interesting but somewhat exotic objects into fundamental components<br />
of galaxy <strong>for</strong>mation and evolution. This change was mainly triggered by the recognition that<br />
supermassive black hole (SMBHs) are ubiquitous in massive galaxies (Magorrian et al 1998).<br />
The striking near-equality between the local black hole mass density and the total density of<br />
matter accumulated through accretion in AGN (Yu & Tremaine 2002) suggests that periods of<br />
nuclear activity may in fact be common phases within galaxy evolution. An intricate link<br />
exists between black hole growth, the <strong>for</strong>mation of galaxy bulges, and nuclear activity cycles;<br />
but most details are still missing from this picture.<br />
This is a challenge to theory and observers alike. In particular, the host galaxy and<br />
environmental properties of AGN at redshifts around and beyond z~1 will allow one to set<br />
strong constraints on <strong>for</strong>mation scenarios. This is an area w<strong>here</strong> MUSE will provide<br />
significant progress, because of its capability to reach very faint flux levels at good spectral<br />
resolution, combined with a high multiplex factor over an astrophysically relevant field size<br />
of ~ 250 kpc. A fundamental advantage of MUSE over existing or other planned instruments<br />
is the integration of the traditional multi-stepped approach of imaging, low-resolution and<br />
high-resolution spectroscopy into a single observation.
Assuming that most of the black hole mass of<br />
present-day galaxies was assembled around<br />
the period of maximum AGN space densities,<br />
between z ~ 1 and z ~ 3 (Wolf et al 2003), the<br />
task is to establish an evolutionary link<br />
between AGN at high z and the local galaxy<br />
population. Such a link can be built by<br />
studying the environments of AGN and<br />
characterising the degree of overdensities they<br />
live in. Luminous radio-loud quasars and radio<br />
galaxies beyond z ~ 1 are typically located in<br />
rather rich structures, probably progenitors of<br />
the most massive clusters today<br />
[REFERENCE]. The environment of lower<br />
luminosity radio-quiet AGN at high z, on the<br />
other hand, is not well constrained. A set of<br />
MUSE pointings on a representative AGN<br />
sample, of a few hours exposure time each,<br />
would yield a complete census of the 100-200<br />
kpc surroundings down to significant sub-L*<br />
luminosities at z=1 and to roughly L* at z=3.<br />
At the same time one would get the velocity<br />
in<strong>for</strong>mation needed to assess the degree of<br />
virialisation in a given structure.<br />
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Figure 2-24: This 1 arcmin x 1 arcmin section of<br />
an HST image in the Chandra Deep Field South<br />
contains 7 X-ray sources, most of which are likely<br />
AGN at intermediate to high redshifts. Some of<br />
these sources were already targeted<br />
spectroscopically with the VLT, but are optically<br />
too faint to give a meaningful spectrum. A single<br />
deep MUSE exposure would not only clarify the<br />
nature of these, but at the same time allow to<br />
study their host galaxies and environments. Image<br />
taken from the GEMS project.<br />
Gravitational interaction and merging are believed by many to be the main drivers <strong>for</strong> driving<br />
nuclear activity. But what exactly are the conditions needed to trigger an AGN? Until today,<br />
the search <strong>for</strong> morphological clues has largely prevailed, but spectroscopic diagnostics can<br />
deliver additional, possibly crucial pieces of evidence. A single MUSE data cube could reveal<br />
also, <strong>for</strong> example, large-scale gas streamers, patterns of enhanced star <strong>for</strong>mation in the AGN<br />
host as well as in other galaxies in the field, and kinematical signatures of recent merger<br />
events, thus provide essential clues about the physical drivers of cosmic AGN evolution.<br />
Most of the sketched AGN studies would have to be per<strong>for</strong>med in pointed mode, targeting<br />
individual pre-selected objects. The "blind" MUSE surveys outlined elsew<strong>here</strong> in this<br />
document provide a chance to integrate the AGN aspect into a multi-purpose survey, by<br />
judiciously selecting survey fields to coincide with deep X-ray pointings. Recent surveys with<br />
Chandra and XMM have yielded surface densities of more than 3 X-ray sources per arcmin2,<br />
a large fraction of which is presumably directly linked to some sort of AGN phenomenon.<br />
These surveys are still largely photon-limited, and even deeper pointings are being considered<br />
which would increase the surface density by at least another factor of 2 (Alexander et al<br />
2003). The suggested concepts of "shallow" and "medium deep" MUSE surveys could in fact<br />
revolutionise the traditional strategy of X-ray imaging/spectroscopic follow up. In particular,<br />
spatially resolved in<strong>for</strong>mation <strong>for</strong> every single X-ray AGN would become available at once,<br />
allowing to deblend the nuclear from the host galaxy spectrum and obtain a much cleaner<br />
spectral diagnostic. At the same time, kinematics and environmental in<strong>for</strong>mation would<br />
become available, with all the benefits mentioned.
Title: Science Case<br />
Reference: MUSE-MEM-SCI-052<br />
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References<br />
Alexander, D.M., et al, 2003, AJ 126, 539-574<br />
Magorrian, et al, 1998, ApJ 115, 2285-2305<br />
Wolf, C., Wisotzki, et al., 2003, A&A 408, 499-514<br />
Yu, Q., Tremaine, S., 2002, MNRAS, 335, 965-976<br />
2.11. The development of dark matter haloes<br />
The fundamental prediction of hierarchical models of structure <strong>for</strong>mation in the Universe,<br />
such as the standard ΛCDM model is that the virialised mass of haloes should grow with time<br />
through the accretion of smaller halos. The prediction from Press-Schechter that the mass<br />
function of virialised structures evolves by increasing the characteristic mass M* while<br />
decreasing the low mass end amplitude is born out by numerical simulations of the dark<br />
matter distribution.<br />
Determining masses of haloes at high redshift is non-trivial. On cluster masses, w<strong>here</strong> the<br />
redshift evolution is at the present epoch strongest (above M* in Press-Schechter) t<strong>here</strong> is a<br />
great sensitivity to cosmological parameters (see SZ section 8) in the comoving density of<br />
bound objects of a given mass as a function of redshift. On galactic masses, around and<br />
below M*, t<strong>here</strong> is a smaller dependence on redshift.<br />
As an integral field spectrograph, MUSE will automatically produce 2-dimensional velocity<br />
fields <strong>for</strong> all emission line galaxies (and brighter absorption line galaxies) in the field of view<br />
(see Section 2.7). A potentially unique capability of MUSE (at significant redshifts) is to<br />
relate the inner and outer halo kinematics at high redshifts, through the velocity dispersion of<br />
satellites 100-250 kpc from isolated massive galaxies (Zaritsky and White 1994, Prada et al<br />
2003). MUSE can be used to identify and measure accurate velocities of all star-<strong>for</strong>ming<br />
satellites around high redshift galaxies. Even a one hour exposure is sufficient to detect at 5σ<br />
a compact (0.8×0.8 arcsec 2 ) line emitting galaxy with a line flux of 4.1×10 -18 erg s -1 cm -2 ,<br />
equivalent to a line luminosity at z ~ 1 of about 2 ×10 40 erg s -1 or a star-<strong>for</strong>mation rate of<br />
about 0.3 M sun yr -1 (Kennicutt 1992).<br />
The goal of this analysis would be to determine M halo (L galaxy ) at z ~ 1, a regime beyond the<br />
range w<strong>here</strong> lensing studies have much leverage (because of the background redshift<br />
distribution). This measurement is automatically combined with measurements of the size<br />
and the rotation curve of the luminous component of the host galaxies.<br />
This science area comes <strong>for</strong> free in all of the survey observations, e.g. the 200 fields of the SF<br />
survey. Additionally, deep redshift surveys, such as VIMOS or COSMOS, could be used to<br />
construct very well defined samples of galaxies, e.g. "isolated" galaxies <strong>for</strong> which this sort of<br />
study is best per<strong>for</strong>med (e.g. Prada et al 2003), <strong>for</strong> observations by the community in GO<br />
mode.<br />
References<br />
Zaritsky and White 1994, ApJ 435, 599<br />
Prada et al 2003, ApJ 598, 260
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2.12. Merger rate<br />
In the hierachical picture of galaxy <strong>for</strong>mation and evolution, galaxies as seen today are the<br />
end product of a long list of merger events. The merger tree as seen in simulations can be<br />
quite complex, and, given a typical merger timescale of several hundred million years, a<br />
galaxy will witness along its life a few major merger when units of similar size / mass<br />
interact, and many more minor mergers with smaller units. As we go back in time, we expect<br />
to witness more of the merger events, as the number of elementary building blocks is<br />
predicted to be larger than today. While we have many examples of galaxy mergers in the<br />
nearby universe, the evolution of the merger rate as a function of look-back time, hence our<br />
understanding of how galaxies build up with time, is still poorly constrained. Current<br />
measurements indicate that the merger rate evolves as (1+z) m , with m=2.5-4 out to z~1. To<br />
better constrain this measurement it is necessary to obtain <strong>for</strong> a large sample of galaxies<br />
representative of the general galaxy population accurate relative velocity in<strong>for</strong>mation of<br />
galaxy companions to predict whether a merger is probable or simply a chance projection. At<br />
redshifts 1-3, measuring the environment of bright galaxies with a velocity accuracy of 10-30<br />
km/s, down to 3 magnitude below M* will allow to map the growing of several hundred<br />
galaxies and strongly constrain the merger rate.<br />
The MUSE Deep Fields will allow measurement of the major merger rate from all interacting<br />
galaxies with a similar mass out to the faintest galaxies in the survey. This should allow to<br />
derive the merger rate with an accuracy of ~10%. Furthermore, as described in section 2.10, it<br />
will be possible to measure the rate of minor mergers from the small satellites around a well<br />
defined sample of galaxies out to a redshift ~1.
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2.13. Survey strategy<br />
The majority of the science goals described in the previous sections can be addressed with the<br />
following staggered survey:<br />
• Shallow field (SF) covering a larger sky area (200 arcmin²) with an 1 hour integration<br />
time by exposure. Note that this survey does not need AO capabilities.<br />
• Medium deep field (MDF) covering a relatively large sky area (40 arcmin²) at<br />
improved depth<br />
• A few deep fields (DF) at random location covering a small area (3 arcmin²) but at<br />
extreme depth (3.9 10 -19 erg.s -1 .cm -2 ).<br />
• Ultra deep field (UDF) using strong lensing to improve the detection limit by a factor<br />
3 or more.<br />
Integ.<br />
Tot. Total Limiting mag. I AB<br />
Field<br />
time by Nb of Area integ.<br />
Limiting Science<br />
Id. Location exp (h) field arcmin² time (h) Full R R/20 flux F subjects<br />
Not yet<br />
SF specified 1 200 200 200 22.2 23.9 50 6<br />
MDF<br />
Random<br />
& QSO 10 40 40 400 23.9 25.5 11<br />
1,3,5,7,9,11,<br />
13,15,17<br />
DF Random 80 3 3 240 25.0 26.7 3.9<br />
1,3,5,7,9,11,<br />
13,15,17<br />
UDF<br />
Lens<br />
cluster 80 2 0.6 160 26.2 27.9 1.3 2,8,13,15<br />
Limiting flux is in 10 -19 erg.s -1 .cm -2 units.
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Science area<br />
Assembly<br />
galaxies<br />
Assembly<br />
galaxies<br />
Assembly<br />
galaxies<br />
Assembly<br />
galaxies<br />
Assembly<br />
galaxies<br />
Assembly<br />
galaxies<br />
Intergalactic<br />
medium<br />
Intergalactic<br />
medium<br />
Intergalactic<br />
medium<br />
of<br />
of<br />
of<br />
of<br />
of<br />
of<br />
Observations<br />
Determination of Ly α luminosity<br />
function and correlation function at<br />
z=[2.8-6.7]<br />
Determination of Ly α luminosity<br />
function and correlation function at<br />
z=[2.8-6.7]<br />
Merger rate<br />
Determination of Ly α luminosity<br />
function (faint end) and correlation<br />
function at z=[2.8-6.7]<br />
Determination of Ly α (very faint<br />
end) luminosity function at z=[2.8-<br />
6.7]<br />
Correlation function of Ly α emitters<br />
at z=[2.8-6.7]<br />
Development of dark matter halo<br />
using velocity dispersion of<br />
satellite galaxies at z~1<br />
Detection of the cosmic web using<br />
Ly α emitters at z=[2.8-6.7]<br />
Detection of the cosmic web using<br />
extended Ly α halos at z=[2.8-3.5]<br />
Detection of the cosmic web using<br />
fluorescent emission<br />
Field<br />
Id.<br />
SF<br />
MDF<br />
DF<br />
UDF<br />
Obj. by field<br />
Nb fields Total<br />
objects<br />
2.8
Title: Science Case<br />
Reference: MUSE-MEM-SCI-052<br />
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Fig. 2-25: Simulated MUSE deep field from GalIcs simulation. Galaxies are coloured<br />
according to their apparent redshift. Galaxies detected by their continuum (I AB < 26.7 )<br />
and/or by their Ly α emission (Flux > 3.9 10 -19 erg.s -1 .cm -2 ) are shown.<br />
For surveys, as opposed to studies of previously identified objects, the power of an integral<br />
field spectrograph relative to a multi-slit spectrograph observing previously identified (i.e.<br />
continuum-selected) objects, is to survey "blank fields". Especially <strong>for</strong> objects with strong<br />
emission lines, such as expected <strong>for</strong> young star-<strong>for</strong>ming galaxies, a survey <strong>for</strong> emission lines<br />
with an integral field spectrograph reaches to extremely faint continuum levels. An emission<br />
line galaxy with line flux 3.9×10 -19 erg s -1 cm -2 at 9200 Å and an equivalent width of 200 Å<br />
(as seen in a good fraction of emission line objects at this wavelength, from Hα at z ~ 0.4,<br />
[OII] 3727 at z ~ 1.4 and Lyman α at z ~ 6.5) has a continuum Z AB ~ 30.0, far below the point<br />
w<strong>here</strong> systematic spectroscopy of continuum-selected galaxies is feasible or attractive<br />
(because most such galaxies would not have detectable lines).<br />
Thus the integral field approach is most attractive (relative to the others) at faint levels and a<br />
MUSE survey should seek to survey down to the faintest possible levels, i.e. well below the<br />
current depth of narrow band surveys (~10 -17 erg s -1 cm -2 ). One consequence of this is that<br />
complementary data to the MUSE data cubes (e.g. imaging and photometry outside of the<br />
MUSE wavelength interval or very high resolution imaging within it) must be<br />
correspondingly deep (AB ~ 30 magnitude) if at all possible.
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The main issue <strong>for</strong> a MUSE survey is the limited field of view (1 arcmin 2 ). The comoving<br />
scale corresponding to 1 arcmin does not change strongly with redshift at z > 2 and is<br />
approximately 2.5 Mpc. For studying the assembly of individual galaxies, surveying scales of<br />
only a few Mpc is sufficient. At turn-around, the 6×10 10 M <br />
of matter which is currently<br />
within the virialized halo of a ~L* galaxy such as the Milky Way is contained within a<br />
volume of radius 750 kpc. Thus a survey field of side 2.5 Mpc should contain all the baryonic<br />
material that will assemble into individual L* galaxies.<br />
The other physical scale of interest is the clustering scale of galaxies, about 5-10 comoving<br />
Mpc. This enters into the issue of sampling variance since it means that the galaxy population<br />
within sp<strong>here</strong>s of this size is highly correlated and the statistics of galaxies are far more noisy<br />
than simple consideration of their numbers would indicate - put another way, the n galaxies<br />
within a sample do not represent n statistically independent entities but rather n/m entities,<br />
w<strong>here</strong> m may be calculated from the correlation function knowing the survey geometry.<br />
Surveys on arc-minute scales are dominated by this sampling variance: a good example is the<br />
very different population of red galaxies in the HDF-N and HDF-S which, on their own would<br />
lead to quite different interpretations of the global star-<strong>for</strong>mation rate.<br />
Given the limited field of view of MUSE, the two strategies <strong>for</strong> overcoming sampling<br />
variance are (a) to observe adjacent contiguous fields to build up a larger area, or (b) to<br />
observe widely separated fields. Of these,<br />
the second is much more efficient: the<br />
statistical weight of the survey builds up as<br />
N 0.5 (w<strong>here</strong> N is the number of MUSE<br />
pointings) w<strong>here</strong>as in (a) the gain is more<br />
like N 0.3 . Thus the optimum survey<br />
strategy would be to observe multiple<br />
widely spaced pointings.<br />
A good feature of this is that this strategy<br />
naturally accommodates the need <strong>for</strong> m ~<br />
17–18 guide stars <strong>for</strong> the AO system.<br />
Un<strong>for</strong>tunately, at present, most of the deep<br />
extragalactic survey fields, and especially<br />
those that have been observed with the<br />
HST) consist of a handful of large<br />
contiguous areas (e.g. GOODS-S 10×16<br />
arcmin 2 ). However, within these, multiple<br />
pointings around available stars could be<br />
made (Fig. 2-26).<br />
Figure 2-26: Potential guide-stars in the CDFS<br />
region, each surrounded by a 90 arcsec radius<br />
region. Axes are decimal degrees in RA and dec
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2.14. A pan-chromatic view of galaxy <strong>for</strong>mation<br />
In this section we describe complementary surveys that should be carried out within the same<br />
volume of space as the MUSE deep fields in order to extract the maximum possible science<br />
from the data. We show that by observing <strong>for</strong> comparable time periods with ALMA, e-VLA,<br />
JWST, and possibly SKA, one can map out the neutral and molecular gas content of the<br />
volume to compare with the ionized gas seen in the MUSE and JWST data, and the starlight<br />
imaging in<strong>for</strong>mation from JWST.<br />
2.14.1. JWST<br />
Thanks to its unrivalled sensitivity in the thermal infrared JWST is designed to be a major<br />
player in the understanding of <strong>for</strong>mation and evolution of galaxies. JWST has a wide spectral<br />
range (0.6-28 µm), but it is only above 1 µm, and probably even above 2 µm, that it shows its<br />
strength with respect to ground based telescopes of similar or larger aperture. Among the 3<br />
instruments, the ESA NIRSPEC spectrograph is particularly well suited to distant galaxy<br />
study because of its multiplex capabilities in the 1-5 µm wavelength range. NIRSPEC is able<br />
to observe simultaneously a maximum of 100 objects in a 3x3 arcmin², at two spectral<br />
resolutions 6 of 100 and 1000. The 2.9-5 µm grating of the R~1000 mode is of special interest<br />
given its almost perfect match in H α redshift range (3.5-6.7) with MUSE Ly α coverage (2.8-<br />
6.7). According to simulations (section 2.2) a MUSE deep field should give 150-200 Ly α<br />
emitters in that redshift range. Depending on the source clustering, in two to four exposures of<br />
15 hours each, NIRSPEC would be able to detect the H α line of all MUSE high z objects 7<br />
with a comparable S/N. Having access to Ly α and H α would not only confirm unambiguously<br />
the redshift of the source, but will give access to dust extinction and star <strong>for</strong>mation rate<br />
measurements. Comparison of line profiles would also tell us about resonant scattering and<br />
velocity shifts of Ly α . Moreover this pre-selection of sources by MUSE should be at least as<br />
efficient as multi-band deep imaging with NIRCAM. The combination of VLT/MUSE and<br />
JWST/NIRSPEC is quite attractive and should strengthen the JWST European scientific<br />
return.<br />
2.14.2. ALMA<br />
The Atacama Large Millimetre Array (ALMA) will provide the principal means of measuring<br />
the rest-frame FIR emission of galaxies as an observed submm/mm continuum, and their<br />
molecular gas content via the CO lines.<br />
With its 64 antennas (each of 12 m diameter), its 16 GHz bandwidth and its first four<br />
receivers covering the 86–116, 211–275, 275–370, and 602–720 GHz bands (be<strong>for</strong>e<br />
completion to a final figure with 10 bands), ALMA will reach at least 100 µJy (5 σ) in an<br />
6 NIRSPEC has another mode with a higher spectral resolution (R~3000) but without multiplex capabilities (only<br />
one single long slit).<br />
7 For the 3.9 10 -19 erg.s -1 .cm -2 MUSE detection limit is able to detect a Ly α line of 2.7 10 -18 erg.s -1 .cm -2 with 85%<br />
obscuration. This translates into 3.1 10 -19 erg.s -1 .cm -2 H α flux, assuming a flux ratio of 8.7 between the two lines.
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hour. It will require 11 (resp. 5, 2) pointings to cover a 1 arcmin 2 field at 350 (resp. 230, 140)<br />
Ghz, and will detect several hundred galaxies arcmin -2 in the continuum and in several<br />
transitions given an hour per pointing (Blain et al. 2000). Since the observation of the Cosmic<br />
Infrared Background (Puget et al. 1996), the detection of a high number of submm sources by<br />
the ISOPHOT and SCUBA instruments, and the discovery of a high UV extinction in Lybreak<br />
galaxies (e.g. Adelberger and Steidel 2000), t<strong>here</strong> has been a growing awareness of the<br />
necessity to study galaxy properties both at optical and IR/submm wavelengths. The energy<br />
emitted by young stars heats up dust and is released at rest-frame IR wavelengths. Thus the<br />
thorough study of the SFR in galaxies requires an accurate assessment of the luminosity<br />
budget. The current and <strong>for</strong>thcoming observations are confusion limited (SCUBA,<br />
SIRTF/MIPS, Herschel/SPIRE, Planck/HFI) and the detected objects at high redshifts are/will<br />
be the so-called LIRGs and ULIRGs, that is, rather extreme objects (with a density of about 1<br />
arcmin -2 at the 2 mJy level at 350 GHz). Only ALMA will be able to have access to the<br />
emission of normal high-redshift galaxies. The GalICS model used in section 2 predicts that<br />
the median flux of MUSE Deep Survey sources at 350 Ghz is 21 µJy. About 25 % of MUSE<br />
Deep Survey sources will be detectable with a dedicated survey of 100 hours per arcmin 2<br />
(typically 10 pointings of 10 h) that reaches 40 µJy (5 σ), with a spatial resolution of 0.2<br />
arcsec, comparable to the one of MUSE. It is interesting to note that, within the assumptions<br />
of the model, almost all the ALMA sources at 2.8
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minimum depth of 5x10-23 Wm-2 (5 sigma), sufficient to detect tens of galaxies with M(H2)<br />
~ 1x10 11 M sun , hundreds of galaxies if line ratios typical of low-excitation conditions prove<br />
common (Blain et al. 2000; Papadopoulos et al. 2001; Papadopoulos & Ivison 2002).<br />
At a 0.3 x L* mass limit, SKA is anticipated to detect 10-20 galaxies in a 1x1' field (actually a<br />
tiny fraction of its field of view) between z=2.5-3.5, several more at an L* mass limit between<br />
z=3.5-4.5 (as well as several hundred between z=1.0-2.5 at far lower mass limits).<br />
The selection of objects in the field would be entirely based on HI, not on the associated<br />
stellar component, and is t<strong>here</strong><strong>for</strong>e independent of the effects of extinction, colour and optical<br />
surface brightness. The combination of deep, HI-selected samples and deep, optically-selected<br />
samples will be extremely powerful <strong>for</strong> studying galaxy evolution over a large range of<br />
redshift.<br />
In addition to HI content, such a survey would also measure the long wavelength radio<br />
continuum emission of the galaxies in the field, which is known to be an excellent indicator of<br />
the massive star-<strong>for</strong>mation rate, independent of the effects of extinction. This in<strong>for</strong>mation can<br />
be used to link the star-<strong>for</strong>mation rates to the HI content of galaxies as a function of redshift<br />
and environment. It will also provide an independent estimate of the evolution of the<br />
comoving star-<strong>for</strong>mation-rate density to be compared with the optically determined functions.
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3. Nearby galaxies<br />
3.1. Introduction<br />
The various studies of high-redshift objects will yield a wealth of in<strong>for</strong>mation concerning the<br />
<strong>for</strong>mation and evolution galaxies. However, the faintness and extremely large distances of<br />
these objects generally prevent detailed studies of the underlying physical processes. For this<br />
reason, interpreting high-redshift observations through the use of simulations and models<br />
relies heavily on the results of work conducted on nearby galaxies. Only by studying and<br />
understanding the local universe will it be possible to determine the complex physics that<br />
shapes the universe at very early epochs.<br />
MUSE will make significant contributions to our understanding of nearby galaxies, making<br />
use of both the high-resolution mode, to resolve the complex structures of galaxy nuclei,<br />
measure black-hole masses, and per<strong>for</strong>m crowded-field spectrophotometry in local objects;<br />
and also of the wide-field mode, allowing sub-kiloparsec scales to be accurately resolved at<br />
distances beyond 100 Mpc, whilst simultaneously providing a global view of entire systems:<br />
ideal <strong>for</strong> relating nuclear properties of galaxies to their outer parts, or accurately mapping<br />
multi-scale phenomena such as galaxy mergers. The large spectral domain of MUSE also<br />
makes it a uniquely versatile instrument, which will herald progress in a diverse range of<br />
science topics in the nearby universe, from stellar dynamics and population studies, to<br />
complex 'gastrophysics' and the properties of AGN.<br />
MUSE will allow quantification of some of the most fundamental processes of astronomy,<br />
which have so far eluded a proper understanding from currently available data. For example,<br />
probing the environment of black holes, as well as determining accurately their physical<br />
properties, will help explain the nature of these phenomena in the global context of galaxy<br />
<strong>for</strong>mation. Connecting stellar dynamics and stellar populations directly with morphological<br />
structure will reveal the true fossil evidence contained in nearby galaxies. Mapping<br />
interacting galaxies on various scales will quantify the impact of merging on galaxy<br />
evolution. And detailed study of star-<strong>for</strong>mation and galactic winds will shed new light on the<br />
question of feedback mechanisms in galaxy <strong>for</strong>mation.<br />
3.2. Supermassive black holes in nearby galaxies<br />
In recent years t<strong>here</strong> has been tremendous progress, primarily from space-based observations,<br />
in our understanding of the distribution of BH masses and the relation between the BHs and<br />
their host galaxies. From such observations, a picture of BH demography has emerged,<br />
summarized by the correlation between BH mass and absolute spheroid luminosity (e.g.,<br />
Kormendy & Richstone 1995; Magorrian et al. 1998) and the much tighter correlation<br />
between BH mass and galaxy central velocity dispersion σ (Ferrarese & Merritt 2000;<br />
Gebhardt et al. 2000). It is now clear that BHs are nearly ubiquitous in galaxies with bulges,<br />
and that their evolution is intimately linked to the evolution of the host spheroid. BH studies
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are now shifting towards higher redshift, generally assuming that the above correlation also<br />
applies in the early universe.<br />
The need to probe the BH radius of influence, inside of which its gravity dominates the stellar<br />
motions, demands sub-arcsecond spatial resolution, even <strong>for</strong> nearby galaxies. Assuming the<br />
BH-σ relation is valid <strong>for</strong> all galaxies, a typical object with central velocity dispersion of<br />
σ~200 km s -1 is expected to contain a BH of mass M BH ~10 8 M ☼ , and this will significantly<br />
affect the galaxy kinematics up to a radius R~0.2”, when observed at the distance of the Virgo<br />
cluster. For this reason most BH masses cannot be reliably measured with ground-based<br />
seeing, and STIS onboard HST has been used <strong>for</strong> the most well-determined BH masses<br />
measured from dynamical modeling of stars or gas within the BH radius of influence.<br />
STIS has some critical limitations, however. Kinematics are only obtained along a single slit,<br />
generally placed across the galaxy centre, and aligned with the photometric position angle. As<br />
a result of this, t<strong>here</strong> is an intrinsic uncertainty in the true orientation of the gas and stellar<br />
kinematic axes. To illustrate this, Figure 1 shows the predicted velocity field <strong>for</strong> a thin disk of<br />
gas orbiting in the combined potential of the stellar density distribution of NGC4660,<br />
computed by deprojecting HST/WFPC2 photometry, and a central supermassive BH of mass<br />
M BH ~10 8 M ☼ as expected from the BH-σ relation <strong>for</strong> this galaxy. It is apparent from the<br />
figure how much a small uncertainty in the position of the slit, with respect to the disk<br />
kinematical axes, can affect the observed kinematics.<br />
Moreover a single slit observation is not<br />
sufficient to detect possible signs of nonaxisymmetry<br />
in the stellar density<br />
distribution, or of non-circular motion in<br />
the gas velocity field. This means that the<br />
symmetry assumptions generally made in<br />
the dynamical models, used to measure the<br />
BH masses, cannot be tested with long slit<br />
data. Multiple slit observations could in<br />
principle be used, to cover a continuous<br />
2D field, but this would lead to<br />
unreasonably long integration times with<br />
the already relatively small 2.4m HST<br />
mirror. Moreover STIS is an ageing<br />
instrument and HST may not be available<br />
much longer.<br />
Another reason <strong>for</strong> the need of high<br />
resolution integral-field data <strong>for</strong> the<br />
determination of BH masses comes from<br />
Figure 3-1: predicted gas velocity field <strong>for</strong> a thin<br />
disk, inclined by i=50°, orbiting the combined<br />
potential of NGC4660, and a central supermassive<br />
BH of mass of 10 8 M ☼<br />
, as in Figure 1. The 0.1”<br />
HST/STIS slit is overplotted <strong>for</strong> comparison. Note<br />
that a very small uncertainty in the positioning of<br />
the slit can dramatically affect the derived gas<br />
kinematics.<br />
simple dimensionality arguments, which suggests that the stellar orbital distribution (e.g. the<br />
anisotropy) cannot be recovered without the knowledge of the line-of-sight velocity<br />
distribution of the stars at all spatial positions on the projected galaxy image on the sky.<br />
Ignorance on the anisotropy directly translates into large uncertainties in the BH mass<br />
determination (e.g. Verolme et al. 2002).
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Figure 3-2: Expected stellar mean velocity (left panel) and velocity dispersion σ (right<br />
panel), <strong>for</strong> a MUSE observation of the elliptical galaxy NGC4660, assuming the galaxy<br />
contains a supermassive BH of 10 8 M ☼<br />
as predicted by the BH-σ relation. The<br />
kinematics was computed by fitting a dynamical model to integral-field SAURON<br />
kinematics and HST photometry. Smoothness was en<strong>for</strong>ced in the intrinsic orbital<br />
distribution to constrain the model at the MUSE higher spatial resolution. Note the<br />
characteristics decrease of σ along the major axis, due to the fast rotating nuclear<br />
stellar disk. A typical galaxy isophote is overplotted with the ellipse.<br />
To simulate the expected quality of the kinematical data obtained with MUSE we generated a<br />
realistic dynamical model <strong>for</strong> the elliptical galaxy NGC4660, with an assumed BH mass as<br />
predicted by the BH-σ relation. The kinematics of the model was then observed at the MUSE<br />
highest sampling of 0.025” per spatial element, properly convolved with a simulated NFM (4<br />
laser guide stars) PSF as obtained at 0.93 µm (Figs 3-2 and 3-3). Detailed calculations show<br />
that, with a 10 hours exposure, MUSE can reach a S/N~30 per spectral resolution element<br />
down to a surface brightness of 13.5 mag arcsec -2 in the I-band. At this central surface<br />
brightness the nuclei of most<br />
nearby early-type galaxies<br />
can be observed. Taking into<br />
account the large number of<br />
spectral pixels sampled by<br />
MUSE this S/N will allow<br />
the extraction of the line-ofsight<br />
velocity distribution<br />
with an error
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significantly better spatial sampling, (iii) the ability to measure the velocity anisotropy, and<br />
(iv) much shorter exposure times, due to its much higher throughput and the order of<br />
magnitude increase of the mirror size of VLT compared to HST. This superiority over STIS<br />
will make it possible <strong>for</strong> the first time to measure accurate BH masses even in giant ellipticals<br />
with extended low-surface brightness cores.<br />
The per<strong>for</strong>mance of MUSE <strong>for</strong> the study of BHs in galaxies is comparable to what can be<br />
obtained with SINFONI, using the SPIFFI integral-field mode in the K band (2.2 µm) and a<br />
natural guide star AO. Similar results should be expected also with the laser guide star mode.<br />
This is as expected, since both instruments have high throughput and would be on the same<br />
8.2m telescope. Our simulations show that the sharper core of the MUSE PSF is somewhat<br />
compensated by a smaller halo in the SINFONI PSF, according to the current PSF estimates.<br />
MUSE however allows observations over a larger spectral range and can detect important<br />
absorption and emission features at optical wavelengths.<br />
References<br />
Kormendy & Richstone 1995, ARA&A, 33, 581<br />
Magorrian et al. 1998, AJ, 115, 2285<br />
Ferrarese & Merritt 2000, ApJ, 539, 9<br />
Gebhardt et al. 2000, ApJ, 539, 13<br />
Verolme et al. 2002, MNRAS, 335, 517
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3.3. Kinematics and stellar populations<br />
Early-type galaxies are thought to have <strong>for</strong>med when the universe was still in its infancy, and<br />
hence provide a wealth of fossil in<strong>for</strong>mation from the evolutionary processes that have shaped<br />
the universe we observe today. Key components of this fossil record are the kinematics of the<br />
system, both of the stars and any gas that may be present; and the distribution of stellar<br />
populations, in terms of their age and chemical composition.<br />
T<strong>here</strong> is observational evidence that early-type galaxies are strongly influenced by recent and<br />
ongoing evolutionary mechanisms. Many galaxies are found to contain kinematically<br />
decoupled components (KDCs), w<strong>here</strong> a significant portion of the galaxy has distinct<br />
dynamical properties from the rest of the galaxy. Moreover, many early-type galaxies exhibit<br />
components with distinct chemical properties, showing a different age and/or metallicity<br />
distribution from the rest of the galaxy. Figure 3-4 illustrates these structures using results<br />
from the SAURON survey (Bacon et al. 2001, de Zeeuw et al. 2002), showing the diverse<br />
kinematic and chemical components which exist in many early-type galaxies, and which are<br />
clearly revealed with integral field spectroscopy. The existence of such substructure within<br />
these objects suggests that early-type galaxies are <strong>for</strong>med hierarchically, through the merging<br />
of smaller systems (e.g. Baugh 1996).<br />
Figure 3-4. Selection of early-type galaxies observed with SAURON. Top row shows the reconstructed<br />
images, which are regular and smooth. The middle row shows the velocity field, and the bottom row shows<br />
the distribution of Mg b absorption strength. Galaxies with strong rotation also exhibit a flattened Mg b<br />
distribution, which is absent in the galaxies with different kinematics. This shows the variety of structures<br />
found in early-type galaxies, and the strong connection between kinematic and chemical galaxy properties.<br />
Models of hierarchical galaxy <strong>for</strong>mation also make strong predictions about the influence of<br />
environment on galaxy evolution. In the deep potential-well of rich clusters, the dense intragalactic<br />
medium strips the reservoir of star-<strong>for</strong>ming material from galaxies, and the high<br />
random velocities of the constituent galaxies inhibits merger events. Galaxies within such<br />
clusters experience their last merging events at high redshift (z ≥ 2), and have since evolved
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quiescently, resulting in old stellar populations. Alternatively in low-density environments,<br />
galaxies can accrete material and experience major merging events at very low redshifts (z
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Figure 3-5 illustrates this, comparing kinematic observations of a galaxy at a distance of 100<br />
Mpc with the equivalent measurements possible with VIMOS. Figure 3-5 (a) shows firstly the<br />
dramatic increase in spatial coverage provided by MUSE. For clusters at distances greater<br />
than 100 Mpc, it will often be possible to survey multiple galaxies in a single field, greatly<br />
increasing the surveying efficiency. Figure 3-5 (b) shows a sub-region of the MUSE field,<br />
containing an input model velocity field of a typical elliptical galaxy at 100 Mpc, overlaid<br />
with isophotes of constant surface brightness. This shows a counter-rotating core with a<br />
velocity amplitude of 60 kms -1 , and a physical size of around 100 kpc, typical of decoupled<br />
cores found in very nearby galaxies. Figure 3-5 (c) shows the same field as observed by<br />
MUSE in the wide-field mode. These observations are based on a 2-hour integration in the I-<br />
band, using the Calcium II triplet region to determine the kinematics. The data have been<br />
spatially binned using the optimal Voronoi tesselation method of Cappellari & Copin (2003)<br />
to obtain a minimum signal-to-noise ratio (S/N) of 30 per spectral resolution element. Figure<br />
3-5 (d) shows the same input field, as it would be observed with VIMOS, using a similar<br />
spatial and spectral sampling. The superior spatial sampling of MUSE is clearly demonstrated<br />
by the ability to resolve the decoupled core.<br />
The extensive wavelength coverage of MUSE, coupled with the relatively high spectral<br />
resolution, will also allow accurate modelling of stellar populations. Several studies have<br />
shown that even dynamically evolved systems like elliptical galaxies can have a significant<br />
spread in the total luminosity-weighted age of their stellar populations (Worthey 1994, Trager<br />
2000). The young ages obtained <strong>for</strong> these evolved systems can be explained by a 'frosting' of<br />
younger stars that contribute a significant amount to the total integrated light, while<br />
constituting only a small fraction to the mass of the total system. In this way, studies based on<br />
the classical line-strength indices, such as the Balmer lines and metal features at visible<br />
wavelengths, are strongly biased towards any young populations that may be present. MUSE,<br />
however, provides continuous coverage from the visible region into the near-infrared,<br />
including in a single exposure many key features <strong>for</strong> stellar population diagnostics. These<br />
features include the major Balmer lines: crucial <strong>for</strong> measuring young stars (in absorption) and<br />
star <strong>for</strong>mation (in emission); so-called 'α-elements', such as Magnesium and Oxygen,<br />
necessary <strong>for</strong> determining stellar<br />
abundances and the enrichment<br />
history of type II super-novae;<br />
the near-infrared Calcium II<br />
triplet: a sensitive measure of the<br />
IMF; as well as numerous Iron<br />
absorption features <strong>for</strong><br />
determining metallicity.<br />
The power of combining these<br />
diagnostics becomes most<br />
apparent when trying to separate<br />
two superimposed populations.<br />
Figure 3-6 illustrates the simple<br />
example of a young (25 Myr),<br />
fast-rotating stellar disk<br />
embedded in an old (11 Gyr)<br />
Figure 3-6. Weighted combination (green line) of a<br />
young (25 Myr: blue line) and old (11 Gyr: red line) SSP<br />
model spectra (Bruzual & Charlot 2003). The young<br />
population contributes around 1% of the mass along the<br />
line of sight.
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non-rotating, pressure-supported spheroidal system. The contribution from the young disk is<br />
weighted such that it contributes only around 1% of the mass along a given line-of-sight, and<br />
is combined with the underlying old population, to give the spectrum given in Fig. 3-6. This<br />
shows that, although the young population dominates at blue wavelengths, the old population<br />
gives the most significant contribution in the near-infrared.<br />
(a)<br />
(b)<br />
Figure 3-7. (a) Rotation velocity (top) and velocity dispersion (bottom) of the young-disk model, as measured<br />
using the Balmer lines. (b) The same as (a), but this time using the near-infrared Calcium triplet to determine the<br />
stellar kinematics. The young, fast rotating disk is clearly visible using the Balmer lines, w<strong>here</strong>as the old, nonrotating<br />
spheroid component is most apparent using the Calcium II Triplet.<br />
Figures 3-7 takes this example one stage further, showing simulated MUSE observations of<br />
the young disk embedded in the old spheroid, simulated <strong>for</strong> a single 1 hour exposure of a<br />
typical elliptical galaxy at a distance of 20 Mpc. Figure 3-7 (a) shows the mean rotation<br />
velocity and velocity dispersion of this two-component galaxy as observed using the spectral<br />
region containing the Balmer lines (3650-4950 Å). Here the rotation of the young disk is<br />
clearly visible, and the dispersion is low, as expected <strong>for</strong> a cold disk component. Figure 3-7<br />
(b) shows the rotation velocity and dispersion <strong>for</strong> the same MUSE exposure, but measured<br />
using the near-infrared Calcium II triplet. At this wavelength, the spectrum has a much higher<br />
contribution from the old, non-rotating spheroid, and the measured rotation is clearly reduced;<br />
likewise, the dispersion is correspondingly higher.
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This simple example shows how the extensive wavelength coverage of MUSE can be used to<br />
investigate one of the key questions in galaxy evolution: how the stellar populations are<br />
related to the dynamics of a galaxy? From the data delivered by a single MUSE exposure, it<br />
will be possible to model in detail the dynamical and chemical composition of galaxies<br />
simultaneously, combining dynamical modelling techniques (such as orbit-superposition or n-<br />
body) with modern stellar libraries and population models. Thus will give tight constraints on<br />
population mixtures and kinematic components, linking a galaxy's morphology, dynamics and<br />
star-<strong>for</strong>mation history directly, in objects spanning the full range of galaxy environment.<br />
References<br />
Bacon, R. et al. 2001, MNRAS, 326, 23<br />
Baugh, C.M., Cole, S., & Frenk, C.S. 1996, MNRAS, 283, 1361<br />
Bruzual, G. & Charlot, S. 2003, MNRAS, 344, 1000<br />
Cappellari, M. & Emsellem, E. 2004, PASP, in press<br />
Cappellari, M. & Copin, Y. 2003, MNRAS, 342, 345<br />
Goto, T., Yamauchi, C., Fujita, Y., Okamura, S., Sekiguchi, M., Smail, I., Bernardi, M., &<br />
Gomez, P.L. 2003, MNRAS, 346, 601<br />
Kuntschner, H., Smith, R.J., Colless, M., Davies, R.L., Kaldare, R., & Vazdekis, A. 2002,<br />
MNRAS, 337, 172<br />
Mehlert, D., Thomas, D., Saglia, R.P., Bender, R., & Wegner, G. 2003, AAp, 407, 423<br />
Trager, S.C., Faber, S.M., Worthey, G., & González, J.J. 2000, AJ, 119, 1645<br />
Worthey, G. 1994, ApJS, 95, 107<br />
de Zeeuw, P.T. et al. 2002, MNRAS, 329, 513
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3.4. Interacting galaxies<br />
The study of galaxies in interaction<br />
has progressed dramatically in the<br />
last decades, showing evidence <strong>for</strong><br />
a number of important processes<br />
occurring during these violent<br />
encounters: gas fuelling from<br />
kiloparsec to parsec scales,<br />
triggering of density waves such as<br />
large scale spirals and bars,<br />
starbursts. Tidal <strong>for</strong>ces are efficient<br />
drivers of violent evolution and can<br />
easily produce bridges and tails,<br />
sometimes ejecting a large quantity<br />
of gaseous and stellar material in<br />
the intergalactic medium. Both the<br />
large-scale structure and the central<br />
Figure 3-8: WFPC2 image of the Antennae galaxy<br />
regions of on-going nearby galactic<br />
interactions are important to examine in detail as they can provide clues on the extent and<br />
distribution of e.g., the dark matter haloes (Bournaud, Duc, Masset 2003 and references<br />
t<strong>here</strong>in), the stellar <strong>for</strong>mation processes in extreme environments (e.g. super stellar clusters,<br />
SSCs; see e.g., Hunter et al. 2000), and more importantly on the building of galaxies in our<br />
hierarchical universe. Interacting systems are also the benchmark <strong>for</strong> our understanding of<br />
their higher redshift representatives.<br />
On-going mergers, like the Antennae galaxies, do fit in this context, and clearly, long-slit<br />
spectroscopy can only provide a biased and limited snapshot of these systems. Only 2D<br />
spectroscopy can reveal the full view of the rapidly evolving merger and e.g. constrain the<br />
interplay between the complex dynamics and the on-going star <strong>for</strong>mation, thus combining<br />
detailed spectra of the newly born/<strong>for</strong>ming clusters with those of the ionized gas medium. In<br />
this context, MUSE can bring unprecedented in<strong>for</strong>mation on a number of exciting issues:<br />
• probing the structure, content and dynamics of the tidal tails and bridges in interacting<br />
systems. This could include the so-called Tidal Dwarfs galaxies (TDGs) which are<br />
observed at the tip of tidal tails, tens of kpc away from the centre of the merging<br />
system. The stellar surface brightness of these structures is low, from 21 to 25<br />
mag.arcsec -2 in the I-band, although reachable with long MUSE exposures. The most<br />
interesting targets <strong>for</strong> MUSE are however the ionized gas structures, associated with<br />
the corresponding tidal features. Recently Ryan-Weber et al. (2003a, 2003b)<br />
confirmed the presence of compact HII regions in the outskirts of galaxies, first<br />
detected via an imaging survey (SINGG, Meyer et al. 2003; see also Sakai et al. 2002;<br />
Gerhard et al. 2002). The luminosities of these regions is around a few 10-16 to 10-15<br />
erg.s -1 .cm -2 , corresponding to a star <strong>for</strong>mation rate of only a few 10-3 Msun/yr. They<br />
are barely detected in the continuum with the SINGG R images having a detection
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limit around 10-18 erg.s -1 cm -2 A -1 . These star <strong>for</strong>ming regions may reveal the tip of the<br />
iceberg of a large reservoir of gas, as they are often observed to be linked to HI tidal<br />
features. Such structures are expected to have been more common in the past, and to<br />
have participated in the enrichment of the intergalactic medium. MUSE could be used<br />
as a true spectroscopic explorer in this context, although it is worth noting that these<br />
sources will be at the limit of what MUSE can target.<br />
• Understanding the <strong>for</strong>mation of super star clusters in tidal tails: SSCs are prevalent in<br />
a number of optical tidal tails and <strong>for</strong> some reason completely absent in others. The<br />
spectroscopic mapping of these clusters in the environment in which they <strong>for</strong>m will<br />
tell us whether the <strong>for</strong>mation of SSCs is linked to the overall mass distribution and<br />
dynamics in the outskirts of the colliding galaxy pairs, or if it is related to local<br />
physical criteria.<br />
• Probing the central regions of merging systems: stellar populations, HII regions, super<br />
stellar clusters (HR and LR). Although a systematic study of such systems along the<br />
Toomre sequence is hampered by e.g., their intrinsic diversity (Laine et al. 2003),<br />
MUSE exposures will allow obtaining exquisite details on the physical conditions<br />
within their central kilo-parsecs.<br />
References<br />
Bournaud, Duc & Masset 2003, A&A, 411, L469<br />
Gerhard et al. 2002, ApJ, 580, L121<br />
Hunter et al. 2000, AJ 120, 2383<br />
Laine et al. 2003, AJ, 126, 2717<br />
Meyer et al. 2003, MNRAS in press<br />
Ryan-Weber et al., 2003a, astro-ph/0311465<br />
Ryan-Weber et al., 2003b, astro-ph/031067<br />
Sakai et al. 2002, ApJ, 578, 842<br />
3.5. Star <strong>for</strong>mation in nearby galaxies<br />
By regulating the stellar, gaseous, chemical, dust and radiant and mechanical energy content<br />
of galaxies, star <strong>for</strong>mation is a driving <strong>for</strong>ce behind their evolution. Yet a fundamental theory<br />
of star <strong>for</strong>mation within galaxies is still missing, which is indeed one of the major obstacles to<br />
building a co<strong>here</strong>nt theory of galaxy <strong>for</strong>mation. Amongst the fundamental unknowns are the<br />
star <strong>for</strong>mation history, efficiency, duration and duty cycle of starbursts of different intensities,<br />
the importance and the dynamical drivers of self-triggering and propagation <strong>for</strong> the spatial<br />
and temporal evolution of the starburst, the impact of starbursts on the host galaxy's stellar<br />
and interstellar medium structure, the feedback onto the evolution of the starburst itself,<br />
whether t<strong>here</strong> are multiple modes of star <strong>for</strong>mation, i.e., in compact dense cluster and in a<br />
diffuse field star <strong>for</strong>mation mode, and clearly the dependence of these unknowns on the local<br />
and global galactic properties, and on the large-scale properties of the environment. In nearby<br />
galaxies, the WF pixel size of MUSE roughly corresponds to the sizes of young stellar<br />
clusters in starburst (Meurer et al. 1995) and normal (Carollo et al. 1998) galaxies, and is<br />
much smaller than the typical diameters of giant HII regions, which are up to about 300 pc<br />
(Oey et al 2003).
Understanding the physical properties of the<br />
gas reservoir from which the stars are <strong>for</strong>med<br />
is key to understanding the physics of<br />
<strong>for</strong>mation of stars. Ionization and shock fronts<br />
through the interstellar medium may cause the<br />
star <strong>for</strong>mation to propagate spatially (e.g.,<br />
Puxel et al. 1997), on timescales which are<br />
likely to depend on both the local physical<br />
conditions as well as the global properties of<br />
the host galaxies. Extinction-corrected line<br />
emission fluxes of hydrogen and metal<br />
<strong>for</strong>bidden lines are needed to construct<br />
diagnostic diagrams such as the<br />
log([OIII]/Hβ) line ratio against the<br />
log([NII]/Hα), log([SII]/Hα), or log([OI]/Hα)<br />
ratios; these diagnostics distinguish photofrom<br />
shock-ionized gas. The presence of<br />
non—photoionized gas has been detected in<br />
long-slit spectroscopic and kinematic studies<br />
(Martin 1998). However, because of the<br />
limited area coverage of long-slit<br />
spectroscopy, this cannot quantify the<br />
prominence and extent of the nonphotoionized<br />
gas within the starbursts. This<br />
limitation is overcome in detailed HST studies<br />
that combine metal- and hydrogen-line high<br />
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Figure 3-9: Example of nuclear star <strong>for</strong>ming ring.<br />
Shown is a HST multi-color image of the center of<br />
NGC 4314 (credit: Benedict et al., and NASA).<br />
Visible are dust lanes, a smaller bar of stars, dust<br />
and gas embedded in the stellar ring, and an extra<br />
pair of spiral arms full of young stars. HR-MUSE<br />
will allow exploring issues such as the connection<br />
between dynamics and star <strong>for</strong>mation properties of<br />
such rings.<br />
spatial resolution data to identify and quantify non-photoionized gas. However, with the<br />
HST, these studies can only be per<strong>for</strong>med with extremely time-costly narrow-band imaging.<br />
As a result, only four starburst galaxies within 5 Mpc have been to date investigated with<br />
HST (Calzetti et al. 2003). In these four starbursts, the fraction of non-photoionized gas<br />
appears to represent at most a 20% of the integrated emission line spectrum. The HST data<br />
suggest however that the galaxy environment plays a crucial role in driving the detailed<br />
structure of the interstellar medium.<br />
By combining large field of view, high spatial and spectral resolution, and broad spectral<br />
coverage, MUSE-WF will be ideal <strong>for</strong> measuring fundamental diagnostics of the emitting gas<br />
which are key to understanding the regulating mechanisms <strong>for</strong> the production and propagation<br />
of star <strong>for</strong>mation at all scales - from the kpc scales of superbubbles and outflows and<br />
superwinds, down to the ~10pc scales which probe the interfaces between the actual sites of<br />
the star <strong>for</strong>mation and the ionization and shock fronts. The few galaxies studied with HST<br />
have typical Hβ, [OIII], Hα and [SII] 1σ detection limits over an area comparable to the WF<br />
MUSE spaxel of about 10 -17 erg s -1 cm -2 . In a 4h integration with the WF of MUSE,<br />
5σ spectra are obtained down to fluxes in the range 1.3 to 5 and 0.3 to 1 10 -18 erg s -1 cm -2 <strong>for</strong><br />
the red and blue lines, assuming a point source or a diffuse emission distribution, respectively.<br />
MUSE will be t<strong>here</strong><strong>for</strong>e generally able to extend such studies to significantly fainter levels of<br />
emission. Such WF MUSE observations will allow to establish whether and how the fraction<br />
of non-photoionized gas depends on galaxy properties by allowing surveying large samples of
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nearby star <strong>for</strong>ming galaxies spanning across the entire parameters space of, e.g.,<br />
morphological types, metallicities, star <strong>for</strong>mation rates and dynamical properties.<br />
Furthermore, even a small fraction of non-photoionized gas is key <strong>for</strong> tracing the location and<br />
morphology of possible large-scale shock structures. Cavities, shells, filaments, concentrated<br />
emission indicate whether and w<strong>here</strong> large amounts of mechanical energy are being deposited<br />
in the interstellar medium, and thus w<strong>here</strong> and how larger-scale phenomena such as<br />
superwinds are likely to originate. MUSE will allow the investigation of the location,<br />
geometry and intensity of such shock structures as a function of local and global –including<br />
dynamical- galaxy properties.<br />
MUSE will also allow studying the star cluster population resulting from and cohabiting with<br />
the reservoir of star <strong>for</strong>ming gas. These young star clusters have been revealed in a variety of<br />
star <strong>for</strong>ming environments which include cooling-flow galaxies, interacting/merging galaxies<br />
(see section 3.4), amorphous peculiar galaxies, and, quite interestingly, ~100pc-scale nuclear<br />
rings embedded in the cores of otherwise normal disk galaxies (e.g., Maoz et al. 2001; see<br />
Figure 3-9). Only with HST imaging it has been possible to resolve the young star clusters in<br />
these rings and study their stellar content. Even <strong>for</strong> nearby galaxies, these clusters are barely<br />
resolved by HST. The ages of the clusters are typically one to a few hundred Myr, their<br />
magnitudes are in the range –10 > M V > -15 and their V-I AB colors are typically between -1<br />
and 2.5. Possibly fed by large-scale dynamical instabilities, such star <strong>for</strong>ming rings are<br />
thought to play a major role in the secular dynamical evolution of disk galaxies and in the<br />
<strong>for</strong>mation of pseudo-bulges by concentrating stellar mass in the nuclear regions (e.g.,<br />
Kormendy & Kennicutt 2004). The HR channel of MUSE will allow the simultaneous<br />
investigation of the reservoir of star <strong>for</strong>ming gas, the stellar content of the young stellar<br />
clusters, and their dynamics. A 4h integration with a modest (3x3) binning of the MUSE-HR<br />
will allow to obtain 5σ spectra down to approximately V~19.2 mag/arcsec 2 , allowing to probe<br />
down to the typical cluster population.<br />
The MUSE studies at optical wavelengths of the on-going and recent star <strong>for</strong>mation will be<br />
complemented by ALMA studies of molecular gas at similar spatial resolution, and by highresolution<br />
ALMA studies of the continuum emission arising from highly obscured regions of<br />
star <strong>for</strong>mation. The in<strong>for</strong>mation provided by MUSE will substantially contribute to building a<br />
physical basis, in terms of internal structure, energetics and evolution, <strong>for</strong> constraining future<br />
simulations -and thus the currently ill-known theory- of star <strong>for</strong>mation, and <strong>for</strong> interpreting<br />
the observations of star <strong>for</strong>ming galaxies at higher redshifts.<br />
References<br />
Calzetti, D., et al., 2003, (astro-ph/0312385)<br />
Carollo, C.M., et al., 1998, AJ, 116, 68<br />
Kormendy, J., Kennicutt, R., 2004, ARAA, in press<br />
Martin, C.L. 1998, ApJ, 506, 222<br />
Maoz, D., et al., 2001, AJ, 121, 3048<br />
Meurer, G.R., et al., 1995, AJ, 110, 2665<br />
Oey, M.S., et al., AJ, in press (astroph/0307230)<br />
Puxley, P.J., Doyon, R., & Ward, M.J. 1997, ApJ, 476, 120
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4. Stars and resolved stellar populations<br />
4.1. Introduction<br />
MUSE will contribute to the understanding of a number of areas which are the subject of<br />
much current research through the observations of marginally resolved stellar groups and<br />
aggregates, and we expect that a large fraction of the stellar community will benefit from this<br />
instrument. We can broadly divide the nearby science cases according to four main groups:<br />
• Young stellar objects, Star-ambient interaction<br />
• Massive spectroscopy (complementarity with GAIA)<br />
• Extragalactic stellar astrophysics<br />
• Extended emission-line ISM/local IGM studies<br />
It is important to stress that MUSE will provide a unique opportunity to pursue extragalactic<br />
stellar astrophysics in galaxies up to several Mpc distant, pioneering a research field and a<br />
technique which will be extended even further with the advent of Extremely Large<br />
Telescopes, such as OWL. MUSE is the research tool of choice to study dense stellar systems:<br />
star-<strong>for</strong>ming regions, star clusters, the Galactic bulge, the Magellanic Clouds, the inner disk.<br />
It is also ideal <strong>for</strong> study of hot ISM/star <strong>for</strong>mation interactions in nearby external galaxies.<br />
4.2. Early stages of stellar evolution<br />
In the early stage of their evolution, stars produce powerful jets and winds. Bipolar atomic<br />
jets are at the same time the most impressive and the most enigmatic phenomenon associated<br />
with the birth of stars. Their structure is highly complex and spans a wide range of scales, as<br />
illustrated in the Figure 4-1, w<strong>here</strong> a bar denotes 1000~AU, or 2 arcseconds at the 500 pc<br />
distance of Orion. It can be seen that the jet:<br />
• is launched and collimated within the innermost parts (< 20 AU) of the circumstellar<br />
disk around the young T Tauri star (cf. HH 30 - top left panel; Burrows et al. 1996)<br />
• develops chains of knots with typical spacing of a few 100 AU and apparent opening<br />
angle of a few degrees (cf. HH34 – top right; Ray et al. 1996)<br />
• undergoes wiggles and large-scale interactions with the interstellar medium or with<br />
previous ejecta through radiative working surfaces (akin to hot spots in extragalactic<br />
jets) known as Herbig-Haro (HH) objects, on a typical scale of 20,000~AU i.e. 40<br />
arcsec at a distance of 500 pc (cf. HH47 - bottom panel; Heathcote et al. 1996).<br />
None of these three phenomena (jet launching, knot <strong>for</strong>mation, wiggles and large working<br />
surfaces) is fully understood at present. Yet, they raise fundamental questions:<br />
• Are stellar jets ejected from the star, its magnetosp<strong>here</strong>, or the inner disk surface<br />
• Could they be the « missing agent » responsible <strong>for</strong> solving the so-called angular<br />
momentum and magnetic flux problems of star <strong>for</strong>mation?<br />
• Do they affect significantly the structure of circumstellar disks, and should they be<br />
taken into account in updated theories of exoplanet <strong>for</strong>mation and migration?
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• Does the jet launching process evolve with protostellar stage, from the embedded<br />
collapse phase to the optically revealed T Tauri phase?<br />
• What is the origin of jet knots and wiggles? Intrinsic variability/precession at the<br />
source or MHD current/kink instabilities in plasma jets?<br />
• Do observed properties agree with theoretical shock models?<br />
• What is the large-scale cumulative impact of stellar jets on the ISM in terms of<br />
turbulence, induced compression, and grain destruction?<br />
Figure 4-1 : HST optical images of jets from young stars. The bar corresponds to 1000 AU, or 2 arcseconds<br />
at the distance of Orion (500 pc). Top left: Jets are launched perpendicular to the accretion disk and<br />
collimated within 20 AU of the central T Tauri star. Top right: Chains of knots with typical spacing of a few<br />
100 AU (0.5'') appear along the jet beam. Bottom: Non-axisymmetric wiggles, filamentary sideways shocks,<br />
and large radiative working surfaces (Herbig-Haro objects) develop on scales of 1000 to 20,000 AU (2''-<br />
40''). [S II] is coded in red and Hα in green<br />
MUSE will provide a powerful new tool <strong>for</strong> the study of large-scale stellar jets: Its wide field<br />
of view can encompass in a single exposure a typical jet and bowshock system such as HH 47<br />
(50 arcseconds across), or the bright inner jet beam of HH 34 (30 arcseconds). Furthermore,<br />
MUSE's optical range is optimal <strong>for</strong> studying atomic stellar jets, which are characterized by a<br />
strong optical emission line spectrum including Hβ, [O III]5007, [N I]5198,5201, [O I]6300,<br />
[N II]6584, Hα, [S II]6716,6731, [CaII]7307, and various [Fe II] lines. Its broad spectral<br />
coverage over 0.465 to 0.93µm will allow simultaneous recording of all lines at each position,<br />
providing extremely accurate line ratios <strong>for</strong> physical diagnostics. For example, the [O
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III]/Hβ ratio is a crucial indicator of fast shocks with speed above 100 km/s, while [S II]<br />
6716/6731, [NII]/[O I], and [SII]/[O I] provide direct estimates of, respectively, the jet<br />
electronic density, ionization fraction and temperature, with much less dependence on the<br />
heating process than ratios involving Hα (e.g. Bacciotti & Eisloeffel 1999). At the same time,<br />
MUSE 's spectral resolution (about 100 km/s) will allow to map the 2D kinematics over the<br />
whole extent of these jets, of typical speeds of 200-500 km/s, to within 10 km/s (line centroid<br />
precision). Finally, MUSE's WFM angular resolution of 0.3–0.4'' will enable to separate<br />
individual emission knots, wiggles, and sideways shocks in the jet beam (cf. Fig. 4-1), which<br />
are otherwise blended in seeing-limited optical studies.<br />
This combination of broad line coverage, kinematics, and high angular resolution over a wide<br />
field of view will represent an outstanding gain in quality and in<strong>for</strong>mation content over jet<br />
studies with other optical instruments: Wide-field spectro-imaging of HH flows with a Fabry-<br />
Perot (see e.g. Morse et al. 1994) is typically limited to 3 lines only (usually [S II] 6716,6731<br />
and Hα) due to the time overhead <strong>for</strong> stepping through each line profile, which severely limits<br />
the physical diagnostics and the shock modelling. Furthermore, the line ratios may be affected<br />
by variations in PSF, sky transmission, and instrumental drifts during the scan. Narrow-band<br />
imaging, e.g. with HST, is contaminated by imperfect removal of stellar light and nebular<br />
emission, and does not allow to resolve the [S II] 6716,6731 doublet nor to separate [N II]<br />
from Hα, precluding density and ionization diagnostics. It also does not give any radial<br />
velocity in<strong>for</strong>mation. Finally, optical spectroimaging with long-slits (eg STIS) is limited to<br />
very narrow jet regions, and clearly cannot cover a large structure such as the HH 47<br />
bowshock, nor probe non-axisymmetric jet features. In addition, uneven slit-illumination<br />
effects introduce spurious gradients that depend on the line and need complex a posteriori<br />
corrections (Bacciotti et al. 2002).<br />
An original, fundamental contribution of MUSE will thus be to routinely provide the first<br />
complete, accurate set of optical line ratios and line centroids at each position of large-scale<br />
stellar jets, with a resolution of 0.4''. A 1800sec exposure will yield a S/N of 50 per 0.2'' pixel<br />
on an Hα line of surface brightness 10 -15 erg.s -1 .cm -2 .arcsec -2 , i.e. 10 times weaker than the 3<br />
bright large-scale jets that can be currently studied at high resolution (HH 34, HH 47, HH<br />
111; cf. Fig. 4-1). This unique capability will open a new dimension in the analysis and<br />
modelling of stellar jets, two domains w<strong>here</strong> ESO research is at world-class level.<br />
Major breakthroughs will result on a number of pressing questions, developed in the<br />
following paragraphs.<br />
4.2.1. The magnetic field strength and shock conditions in the jet<br />
An important outcome of MUSE will be to constrain the shock speed, preshock density, and<br />
magnetic field strength as a function of position and velocity in large-scale jets, from<br />
comparison of resolved optical line ratios with grids of atomic shock models (see e.g.<br />
Hartigan, Morse, Raymond 1994). A similar method was used to estimate the magnetic field<br />
in the ambient gas, from seeing-limited studies of large jet bowshocks (e.g. Morse et al.<br />
1992). MUSE will yield the magnetic field strength in the jet, a crucial constraint <strong>for</strong> MHD<br />
ejection models. Its combined high angular resolution and spectroscopic resolution will be<br />
essential to avoid blending of individual jet knots, which would otherwise bias the line ratios.
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An illustration of this point can be found in Lavalley-Fouquet et al. (2000): While integrated<br />
line ratios at the base of the DG Tau jet could not be modelled with a single shock (Hartigan<br />
et al. 1995), spatially and velocity-resolved lines ratios at 0.4'' resolution obtained with the<br />
OASIS spectro-imager are well fitted with internal shocks of speed of 30-80 km/s and a<br />
transverse magnetic field < 1000 µG.<br />
4.2.2. Jet total density and the ratio of ejected to accreted mass<br />
While estimates of jet mass-loss rate from integrated line fluxes appear uncertain by 1-2<br />
orders of magnitude, accurate values may be derived from local estimates of the velocity and<br />
of the total density, derived from optical line ratio diagnostics of the electronic density and<br />
ionization fraction (e.g. Cabrit 2002). With the sensitivity of MUSE, this approach can be<br />
applied to many more jets than the favorite 3 targets of current detailed studies. MUSE will<br />
thus provide <strong>for</strong> the first time accurate mass-loss rates as a function of position and velocity in<br />
a representative sample of jets, allowing a major improvement in the determination of the<br />
ejection to accretion ratio - another crucial parameter <strong>for</strong> theoretical ejection models -.<br />
4.2.3. The origin of jet knots and non-axisymmetric wiggling<br />
structures<br />
MUSE will provide <strong>for</strong> the first time the 2D velocity field in large-scale jets at a resolution of<br />
0.3–0.4'', and even the full 3D-field when combined with proper motions from multi-epoch<br />
observations. These observations will probably represent the strongest tests ever <strong>for</strong> the two<br />
competing models of knot <strong>for</strong>mation, namely: propagation instabilities (K-H, current-driven,<br />
kink modes...) versus source variability (precession, velocity variability, orbital motions),<br />
through comparison with the 2D and 3D hydrodynamical and MHD jet simulations conducted<br />
by european teams, and laboratory laser beam experiments. This modelling will also constrain<br />
the MHD cross-section of the jet, or the timescale and amplitude of intrinsic jet variability,<br />
providing indirect clues to the ejection process.<br />
4.2.4. Low-velocity halo and relation to molecular jets<br />
Both the HH 47 jet (Hartigan et al. 1993) and the small-scale jet from DG Tau (Lavalley et al.<br />
1997; Bacciotti et al. 2000) possess a lower velocity halo surrounding the fast, bright optical<br />
jet beam. It is yet unclear whether this halo traces a slow wind ejected from several AUs in<br />
the disk, or a shocked cocoon created by interaction of the jet with the ambient medium.<br />
MUSE's high sensitivity will allow to trace this slow component further away from the jet<br />
axis, estimate its momentum flux, and investigate its relationship to molecular counterparts<br />
studied in H2 lines in the near-IR (e.g. with SINFONI) and in CO lines with ALMA. Such<br />
studies will be crucial to understand the <strong>for</strong>mation of molecular flow cavities, which appear to<br />
require a wider wind component around the collimated optical jet, and to constrain the<br />
outermost disk radius affected by the ejection process.
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4.2.5. The physics of jet working surfaces and interstellar shocks<br />
2D maps of the kinematics and line ratios in jet working surfaces at 1.3'' resolution, obtained<br />
with F-P imagers, reveal good agreement with theoretical expectations <strong>for</strong> a bowshock and jet<br />
Mach disk, and constrain the ambient velocity and magnetic field ahead of the bowshock, as<br />
well as the jet/ambient density ratio (Morse et al. 1992; 1993; 1994). However, these studies<br />
meet several limitations; the H α line flux used to derive preshock density depends on the illknown<br />
pre-ionization and reddening; the cooling regions are spatially resolved (0.5'' to 1''),<br />
introducing a shift between Hα and [SII] emission that complicates interpretation of the line<br />
ratio; only the brightest 3 jets in the sky can be studied in a reasonable time. MUSE<br />
observations will revolutionize this domain by providing a wealth of reddening-independent<br />
line ratios <strong>for</strong> shock diagnostics, an angular resolution higher by a factor 3, and access to a<br />
more representative sample of jets. Expected outcomes include: detailed tests of interstellar<br />
shock models by comparison with observed cooling distances and line offsets, accurate<br />
estimates of the jet mass flux at the Mach disk and of the momentum transferred to the<br />
ambient cloud, evaluation of elemental depletion (using e.g. [Fe II]/[S II] ratios) as signatures<br />
of grain destruction in shock waves, implications on molecule re<strong>for</strong>mation in the compressed<br />
post-shock gas...<br />
4.2.6. Jets in pre-planetary nebulae<br />
Optical jets associated with shocks and HH objects have been recently observed in young<br />
bipolar planetary nebulae (e.g. by HST) suggesting that collimated mass-loss occurs in dying<br />
stars as well. The unique capabilities of MUSE are also perfectly suited to probe this<br />
enigmatic mass-loss process at the other extreme of stellar life, which is also far from<br />
understood.<br />
4.2.7. High-resolution studies of the jet base<br />
The high-resolution mode of MUSE is perfectly suited to complement studies of the<br />
innermost regions of jets with ALMA and SINFONI. In the mm range, ALMA will trace the<br />
cool (< 500 K) molecular flow at very high spectral resolution (0.1 km/s). In the near-IR,<br />
SINFONI will trace warmer molecular gas (2000 K) in H2 as well as hot atomic jets in [Fe II]<br />
and He I, with 75 km/s resolution. MUSE will trace the same atomic component at similar<br />
spectral resolution, but over a much larger field of view (7.5'' instead of 0.8'' <strong>for</strong> SINFONI in<br />
its 25mas mode). This unique feature will allow e.g. to follow the appearance and spacing of<br />
individual knots as they propagate along the jet, and to investigate the origin of enigmatic<br />
broad wind bubbles, such as that seen in XZ Tau (4'' in size; Krist et al. 1999). In a 3600sec<br />
exposure, MUSE will reach a S/N of 30 <strong>for</strong> an Hα brightness of 1.6 10 -14 erg.s -1 .cm -<br />
2 .arcsecond -2 , typical of the XZ Tau bubble and of T Tauri jets at 0.5'' from the star. A S/N of<br />
7 will be achieved <strong>for</strong> 10 -15 erg.s -1 .cm -2 .arcsecond -2 , allowing to probe more distant regions, or<br />
fainter lines. Another complementary feature of MUSE is its wide spectral band, including<br />
powerful density, temperature and ionization diagnostics. The innermost (< 0.5'') regions of T<br />
Tauri jets are bright enough in the optical (up to 10 -13 erg.s -1 .cm -2 .arcsecond -2 in [O I]6300) to<br />
be detected by MUSE in a variety of line diagnostics. Serendipitous line detections may also<br />
show up in this wide band, which has never been completely explored in stellar jets.
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4.3. Massive spectroscopy of stellar fields: our Galaxy and<br />
the Magellanic Clouds<br />
A continuing challenge <strong>for</strong> observational astrophysics is the detailed study and understanding<br />
of the star <strong>for</strong>mation and the chemical history of the Galaxy and of its nearby companions,<br />
such as the Magellanic Clouds. T<strong>here</strong> is the opportunity <strong>for</strong> a substantial European<br />
astronomical community leadership in this crucial science, by combining appropriate<br />
instrumentation at ESO with the <strong>for</strong>thcoming ESA GAIA mission (see, e.g., Perryman et al.<br />
2001 <strong>for</strong> a more comprehensive presentation of the GAIA science cases). GAIA will provide<br />
high spatial resolution (0.2arcsec) and precision astrometric data <strong>for</strong> the whole sky to V=20.<br />
By complementing this in<strong>for</strong>mation appropriately, we will be well placed to make<br />
quantitative advances in addressing basic questions: How did our galaxy and its satellites<br />
<strong>for</strong>m? How have they evolved? What is the stellar population history of the Galactic Bulge?<br />
The answer to these basic questions requires an enormous observational ef<strong>for</strong>t, but can be<br />
done in detail at low redshift, to calibrate and complement the direct studies at higher redshift.<br />
While massive photometry surveys (MACHO, EROS, 2MASS, DENIS, VST, VISTA) have<br />
paved the road towards a better census, most of the fundamental kinematics and spectroscopic<br />
in<strong>for</strong>mation is so far missing. Without this, our knowledge will necessarily remain limited,<br />
with no adequate inclusion of chemical abundances, useful ages, or the critical kinematics,<br />
mapping both the gravitational potential and the orderliness (or otherwise) of accretion and<br />
evolution: these limitations can be seen <strong>for</strong> example, from the restrictive analysis possible of<br />
even the massive photometry data sets in the LMC/SMC (Zaritsky et al.1999).<br />
4.3.1. The astrophysics of crowded regions and GAIA<br />
complementarity<br />
The GAIA mission will ultimately measure parallaxes and proper motions <strong>for</strong> a billion stars<br />
up to V~20 with unprecedented accuracy, and will obtain radial velocities <strong>for</strong> relatively<br />
isolated bright (V
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will allow spectroscopy of the X-ray candidates, to confirm their nature, and to measure and<br />
determine their orbital parameters. Similarly, spectroscopy could reveal the nature of the<br />
many blue stragglers and blue objects revealed in the HST images of the core of 47 Tuc<br />
(about 100 objects found by Ferraro et al. 2001) , and alleviate the current bias to extremely<br />
hot objects: it is reasonable to assume the existence of strange cool objects too. It may even be<br />
possible to understand the anomalous evolution of globular clusters recently discovered<br />
(Mackey and Gilmore 2003), w<strong>here</strong> it seems core evolution proceeds in the opposite sense to<br />
that expected from dynamical predictions with no allowance <strong>for</strong> physical interactions.<br />
The key experiment <strong>here</strong> is dynamical mapping of the inner regions of Globular Clusters<br />
across the full age range uniquely available in the Magellanic Clouds. Such data would<br />
determine kinematic distribution functions, binarity, mass length scales, the incidence of<br />
extreme objects, the age-dependance of core mass-transfer hard binaries, and so on, providing<br />
a unique view of the dynamical evolution of dense systems.<br />
Figure 4-2: The inner Galaxy extinction map, derived from DENIS survey data (Schultheis etal 2000). The many<br />
areas of low extinction, on a scale of the MUSE fov, are apparent, illustrating that quantitative dynamical and<br />
stellar population studies of the inner Galactic bulge and Old Disk, are feasible using optical spectroscopy.<br />
Essentially nothing is understood of the evolution of the dense inner Galactic Bulge, clearly a<br />
site of continuing massive star <strong>for</strong>mation, w<strong>here</strong> sufficiently many optical windows are<br />
known to allow short-wavelength studies (see Launhardt, Zylka and Mezger 2002; and Yusef-<br />
Zadeh, Melia and Wardle (2000) <strong>for</strong> recent overviews of the inner bulge astrophysical zoo).<br />
In all these cases, it is the combination of field of view – ideally matched to the physical<br />
scales of relevance – and full 2-D sampling, allowing deconvolution of disparate sources,<br />
which makes the science viable. This same science of course can be extended, at decreasing<br />
physical spatial resolution, to other nearby galaxies and their nuclei.<br />
Many other fields exist <strong>for</strong> which MUSE will allow detailed astrophysical analyses, provided<br />
that massive spectroscopic studies are available. Fields in the Magellanic Clouds and in the<br />
Galactic bulge are obvious candidates, because these aggregates are close enough to allow<br />
the sampling of a good fraction of the Colour Magnitude diagram and at the same time they<br />
represent unique stellar systems.
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4.3.2. Surveying the Large<br />
Magellanic Cloud<br />
As a close companion to our Galaxy, the<br />
Large Magellanic Cloud has been under<br />
extensive scrutiny with studies focusing on a<br />
broad range of scientific issues, including e.g.,<br />
star <strong>for</strong>mation regions, micro-lensing, HI<br />
structure, calibration of the distance scale...<br />
Considering the simultaneous spectral and<br />
spatial coverage, MUSE could significantly<br />
contribute to our understanding of the stellar<br />
populations and dynamics of this galaxy.<br />
Apart from a better handle on the stellar<br />
populations and the corresponding star<br />
<strong>for</strong>mation history of the LMC itself<br />
(influenced by past encounters with our<br />
Galaxy?), MUSE data on the LMC could<br />
provide a unique handle on its intrinsic<br />
structure. The LMC is indeed a complex<br />
object, with e.g., an offset bar lying near, but<br />
not at, its centre (see van der Marel et al.,<br />
2002; and references t<strong>here</strong>in) and the lack of<br />
kinematic data is only emphasizing it more.<br />
Only about 1000 carbon stars so far have<br />
their radial velocities measured to yield<br />
some constraints on the line-of-sight<br />
kinematics of the LMC (see e.g. Alves &<br />
Nelson, 2000). A more detailed knowledge<br />
of the LMC stellar population, internal<br />
kinematics and morphology will have<br />
important consequences on scenarios <strong>for</strong><br />
galaxy <strong>for</strong>mation, the <strong>for</strong>mation of our own<br />
Galaxy halo, results from micro-lensing, etc.<br />
The full spectroscopic mapping of even just<br />
the central bar about 3x0.5 degrees) would<br />
ask <strong>for</strong> a prohibitive amount of telescope<br />
time. However, a ‘sparser’ approach in<br />
terms of spatial locations of the fields could<br />
uniquely probe the LMC structure, with only<br />
a reasonable scientific loss due to the noncontiguity<br />
of the fields. According to the<br />
luminosity function derived by Smecker-<br />
Hane et al. (2002), we expect a density per<br />
MUSE field (1 arcmin 2 ) and per magnitude<br />
bin of roughly a few stars at V=19 and more<br />
Figure 4-4: Colour magnitude diagrams obtained<br />
with WFPC2 observations. A) Disk field about 2<br />
degrees from the center of the LMC bar and b) the<br />
bar field. Extracted from Smecker-Hane et al.<br />
2002. Panels c) and d) magnify the red clump<br />
region.<br />
Figure 4-3: Main sequence luminosity<br />
function of the LMC in the bar and disk<br />
fields observed by Smecker-Hane et al.<br />
(2002). Bin size are 0.05 mag. Model<br />
luminosity functions are also provided<br />
(constant star <strong>for</strong>mation rate – solid lines,<br />
see Smecker-Hane et al. 2002 <strong>for</strong> details).
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than 100 stars at V=22 mag within the bar of the LMC (see also Elson et al. 1997). This<br />
obviously decreases rapidly outwards, with typical density 10 times smaller in the disk of the<br />
LMC. In order to observe tens of stars in a single MUSE exposure a few degrees from the<br />
centre of the LMC bar, we need to reach V=22.5 mag, which is feasible with short exposures<br />
of less than 600s in the WFM, at a spectral resolution of 500 (using the NoAO mode with<br />
‘’good’’ observable conditions, and spectral binning). Conversely, this will bring hundreds of<br />
stars per MUSE exposure in the central bar region, without the need to spectrally bin <strong>for</strong> the<br />
brightest ones.<br />
As shown in the colour-magnitude diagrams of e.g., Smecker-Hane et al. (2002), a limit of<br />
V=22.5 mag will allow to reach stars 1.5 magnitude below the oldest main-sequence turnoffs<br />
in the LMC. A knee is observed in the luminosity function of both the disk and the bar around<br />
V~22.2 mag. T<strong>here</strong> are also a number of spikes in the bar luminosity function around V=21.5,<br />
20.6 and 19.7, indicating large temporal variations in the star <strong>for</strong>mation rate, all easily<br />
reachable with short (few mn) MUSE exposures. A large observation campaign aimed at<br />
probing both the bar and disk stellar populations and kinematics (with different exposure<br />
times) would thus provide an unprecedented (and simultaneous) view at the star <strong>for</strong>mation<br />
history and internal structure of the LMC. Note that the use of AO would certainly minimize<br />
the potential blending effect, and that the spectral in<strong>for</strong>mation provided by MUSE will also<br />
allow a relatively easy decontamination from <strong>for</strong>eground Galactic sources.<br />
The main goal of such an ambitious project would be to 1) obtain spectral in<strong>for</strong>mation of stars<br />
spanning a significant coverage (statistically speaking) of the HR diagram, significantly<br />
below the oldest main sequence turnoffs, and down to the observed ‘’knee’’ at V=22.2 mag<br />
hence constraining the entire star <strong>for</strong>mation history of the LMC, 2) spatially cover both the<br />
disk and the bar of the LMC hence properly constraining the intrinsic structure of the galaxy<br />
and its link to its stellar population (e.g., the hypothesis that the bar <strong>for</strong>med 1 to 2 Gyr after<br />
the disk). This goal requires spectra <strong>for</strong> at least 50 000 stars, with the entire visible spectral<br />
Fig. 4-5: Combined FORS (Red) and HST(Blue) images of the young LMC Cluster NGC1850; emission<br />
line filaments (Hαl ) are clearly present; the small group of hot stars below the main cluster (NGC1850B) is<br />
younger, only a few Myrs old. Narrow band photometry has revealed a population of T-Tauri candidates,<br />
lying preferentially along the filaments (Romaniello et al. 2002). Only spectroscopy can probe their nature.
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domain at a resolution R > 800 (and up to 3000 <strong>for</strong> the brightest ones). Most of these stars<br />
will be fainter than V = 20 mag, hence this calls <strong>for</strong> a large telescope aperture. VIMOS, in its<br />
IFU mode, would not be efficient enough (field is too small <strong>for</strong> the 0.33 arcsec per fiber<br />
mode, at intermediate spectral resolution around R=700), would require long exposure time (><br />
30 mn) to reach the desired magnitude limit (V=22.5), and would only cover part of the<br />
visible spectral domain. The MOS mode of VIMOS is also excluded because of its low<br />
overall efficiency with the need of pre-imaging, its limited spectral coverage and its inability<br />
to cope with dense fields.<br />
Using the constraints mentioned above, we can make a first estimate of the amount of<br />
telescope time to be devoted to such a survey of the LMC stellar populations and structure: it<br />
would require about ¼ of a square degree (1000 individual MUSE fields, separated by about<br />
15 arcmin on average) with an average of about 8 mn exposure time, hence a total of about<br />
135 hours.<br />
In Figure 4-5 a composite FORS and HST image of the NGC1850 cluster in the LMC is<br />
shown (Romaniello et al. 2002). Clusters like these represent unique chances <strong>for</strong> studying<br />
star <strong>for</strong>mation in action, as well as in its later `feedback’ phase reheating the ISM: critical<br />
in<strong>for</strong>mation to improve galaxy <strong>for</strong>mation recipes. Such objects are very rare, are large in area,<br />
are crowded, and are complex stellar and gaseous environments. While the main cluster is<br />
several tens of million years old, the blue aggregate just below (NGC1850B) probably<br />
represents a much younger star <strong>for</strong>mation region. Was the star <strong>for</strong>mation in the young cluster<br />
triggered by shocks from the older one? Does a population of lower mass stars (T-Tauri) exist<br />
and what is its IMF? Did the <strong>for</strong>mation of young low mass stars preferentially take place<br />
along the filaments created by the SN shocks? To answer all these questions, 3D spectroscopy<br />
is necessary, coupled with high angular resolution; in cases like this 3D is much superior to<br />
single object spectroscopy because it will allow one to simultaneously map the emission gas,<br />
derive its dynamics and to disentangle the gas<br />
Hα emission from that of the T Tauri<br />
candidates: ie, to quantify `feedback’.<br />
Most of these sources are relatively bright, so<br />
that very long exposures are not required:<br />
rather, high S/N studies will be possible. The<br />
unique contribution of MUSE is in combining<br />
high image quality with areal coverage,<br />
essential <strong>for</strong> progress when the answer is not<br />
known in advance, since<br />
deconvolution/modelling of the actual<br />
luminosity distribution in the field under the<br />
seeing conditions of observation is critical <strong>for</strong><br />
the science: ie, quantitative IFU imagingspectroscopy<br />
is critical.<br />
Figure 4-6: The current state of knowledge of corecollapse<br />
supernovae progenitors. Only three good<br />
identifications are known, two discovered in late<br />
2003. A systematic study of massive stellar<br />
populations with MUSE would quantify this figure,<br />
and quantify the origin of compact objects: neutron<br />
stars and black holes – in the Universe.
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4.3.3. Supernovae remnants<br />
The field around SN1987A is an excellent example: in this field HST photometry starts to<br />
unveil the nature (and reddening) of some 21000 stars down toV~24 (about 400 stars.arcmin -2<br />
at V=22, Panagia et al. 2001); needless to say that MUSE (+AO) spectroscopy could confirm<br />
the photometric results, but more importantly determine the age distribution of the stars in the<br />
SN1987a field. This, in turn, will permit one to determine if the SN progenitor was part of a<br />
12 Myr old loose cluster as suggested by the HST photometry. More generally, Smartt etal<br />
(2004) and Maund etal (2004) have proven a method to identify the precursors of TypeII<br />
supernovae, by (HST) imaging of nearby star-<strong>for</strong>ming near face-on spiral galaxies. This<br />
technique has already led to the first planned discoveries of SN precursors: a MUSE<br />
spectroscopic survey to complement the available multi-colour imaging would revolutionise<br />
not only knowledge of the very late stages of stellar evolution, but extend studies of massive<br />
star <strong>for</strong>mation into a systematic stage of quantitative exploration across the spiral sequence.<br />
Fig 4-7: M81, host to SN1993J, whose surviving binary companion star is shown. Studies such as these,<br />
which identify supernova precursors from archival imaging, could be made quantitative through a massive<br />
spectroscopic survey of nearby star-<strong>for</strong>ming disks. [from Maund etal 2004]<br />
4.4. Massive spectroscopy of stellar fields: The Local group<br />
and beyond<br />
The study of resolved stellar populations in galaxies out to the distance of the Virgo cluster<br />
has become a major science case <strong>for</strong> the proposed new generation of OWL and other<br />
Extremely Large Telescopes (Hawarden et al. 2003, Najita & Strom 2002, Wyse et al.<br />
2000). MUSE will contribute dramatically to the study of galaxy origins and evolution by<br />
surveying large volumes of the distant, early Universe. In parallel, only the investigation of<br />
nearby galaxies through detailed analysis of their stellar populations, resolved into individual
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stars, can provide quantitative templates <strong>for</strong> the calibration of integrated light studies of<br />
higher redshift systems.<br />
Pioneering work (Fig. 4-8) with conventional MOS techniques has shown that these<br />
observations are extremely challenging due to source confusion in crowded stellar fields and<br />
severe contamination from gaseous emission of the ISM. Integral field spectroscopy has the<br />
unique potential to overcome these limitations, applying, in principle, the same methods<br />
which have been developed so successfully <strong>for</strong> crowded field CCD photometry (e.g.<br />
DAOPHOT). As an additional asset, IFU surveys in nearby galaxies will provide a wealth of<br />
serendipitous discoveries, in particular emission line stars, novae, planetary nebulae and H II<br />
regions, luminous Xray sources, etc.<br />
Fig. 4-8 Resolving galaxies into stars: one degree field of local group galaxy M33 with LBV<br />
candidate star B416 and surrounding nebula. Prototype 3D spectroscopy in the highlighted<br />
15”x16” field, conducted at the Selentchuk 6m telescope, has demonstrated the superiority of the<br />
method over conventional slit spectroscopy.<br />
The conventional analysis of stellar populations in external galaxies <strong>for</strong> star <strong>for</strong>mation<br />
histories and chemical enrichment using the classical methods of resolved stellar CCD<br />
photometry on the one hand, and integrated-light broad band colors or absorption line indices<br />
on the other, suffers from well-known shortcomings such as the age-metallicity degeneracy,<br />
and uncertainties from the presence of dust and ionized gas in the interstellar medium of the<br />
galaxy under study (dust effecting the surface photometry through extinction, gaseous<br />
emission filling in the absorption line profiles of Hβ, Mg b , Mg 2 ). Other observational<br />
limitations <strong>for</strong> absorption line indices are related to systematic errors of long-slit spectroscopy<br />
(Mehlert et al. 2000).
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A more recent alternative approach is<br />
based on the spectroscopic analysis of<br />
individual resolved luminous stars in<br />
nearby galaxies, e.g. M31 (Smartt et al.<br />
2001, Venn et al. 2000), NGC6822<br />
(Venn et al. 2001), M33 (Monteverde et<br />
al. 1997), or NGC300 (Urbaneja et al.<br />
2003). Using VLT + FORS, the<br />
feasibility of high signal-to-noise stellar<br />
spectroscopy even beyond the local<br />
group was demonstrated by Bresolin et<br />
al. (2001), who measured 7 supergiants<br />
of spectral types B, A, and F with<br />
V≈20.5 in NGC3621 (d=6.7 Mpc). For a<br />
review on extragalactic stellar Fig. 4-9: Removing nebular contamination from<br />
stellar spectrum using cplucy<br />
spectroscopy, see Kudritzki 1998.<br />
Using its potential <strong>for</strong> crowded field spectroscopy, which is superior to any other conventional<br />
technique, MUSE will explore the emerging field of extragalactic stellar spectroscopy as an<br />
important step towards the optimal use of the combination of light-collecting power and<br />
angular resolution of these future telescopes, whose importance <strong>for</strong> applying the wellestablished<br />
methods of quantitative stellar spectroscopy to stars in galaxies outside of the<br />
Milky Way must be stressed as one of the major innovations in astrophysics of the next<br />
decades.<br />
The main argument is that the knowledge of the point-spread-function (PSF) of a stellar<br />
object can be used to apply PSF-fitting techniques, thus discriminating the source against the<br />
background ⎯ analogous to PSF-fitting CCD photometry, which has been so successful <strong>for</strong><br />
the construction of globular clusters CMDs and the photometric study of resolved stellar<br />
populations in nearby galaxies (Mateo 1998). The novel technique has been pioneered with<br />
relatively small present-day IFUs and limited angular resolution (Roth et al. 2003, Becker et<br />
al. 2003). These studies have demonstrated the unique capabilities which can be expected<br />
from the 1 arcmin FOV of MUSE, sampled at 0.2” spatial resolution (or its equivalent in the<br />
Narrowfield Mode).<br />
Becker et al. (2003) have processed datacubes of the LBV candidate star B416 with its<br />
surrounding nebula in M33 using the cplucy two-channel deconvolution algorithm to separate<br />
the stellar spectrum from a spatially unresolved nebular component (Fig.4-9). This technique<br />
makes use of the spatial resolution of an HST image of the same field, providing <strong>for</strong> an<br />
accurate model of the heavily blended stellar field from the ground-based 3D observations.<br />
Fig. 2 shows how it was possible to accurately subtract from the stellar spectrum the<br />
contaminating [O III] λ4959, λ5007 emission lines, revealing He I λ5015 and a blend of Fe I<br />
lines. This result would have been impossible to obtain from conventional slit spectroscopy,<br />
demonstrating that the 3D method opens entirely new opportunities <strong>for</strong> crowded field<br />
spectroscopy.
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The correction <strong>for</strong> nebular contamination is a pressing issue <strong>for</strong> the quantitative spectroscopy<br />
of massive stars in nearby galaxies, limiting very severely our ability to provide the badly<br />
needed statistics to shed light on stellar evolution <strong>for</strong> masses > 10 M◉ , which is theoretically<br />
poorly understood. Likewise, abundance studies of extragalactic planetary nebulae, which<br />
provide important in<strong>for</strong>mation about star <strong>for</strong>mation histories and chemical enrichment, suffer<br />
dramatically from systematic errors due to background subtraction problems in high-surface<br />
brightness regions of local group galaxies and beyond. Large area, high spatial resolution 3D<br />
spectroscopy is the clue to solving these observational problems. The two examples are<br />
discussed in more detail in the sections below.<br />
A deep mosaic survey over 5x5 arcmin 2 with a total observing time of 100 hours per galaxy<br />
will result in an unprecedented inventory of O-B-A supergiants, rare<br />
LBV−WN/Ofpe−B[e]−WN−WC stars, planetary nebulae, and H II regions <strong>for</strong> any galaxy of<br />
the Fornax group, providing simultaneously :<br />
• complete spectroscopic samples <strong>for</strong> the quantitative study of these object classes<br />
• a unique database <strong>for</strong> the calibration of long-range integrated-light stellar population<br />
diagnostics, based on first principles (accurate abundances, ages, and kinematics from<br />
individual stars/nebulae)<br />
Note that the survey will be extremely efficient in that it replaces the conventional way of<br />
targeted observations <strong>for</strong> any single object class by a single campaign. For example, the<br />
Massive Stars and PN science cases as described below are covered by the same survey. In<br />
addition, data mining will provide spectra <strong>for</strong> other objects like SNR, novae, ultra-luminous<br />
X-ray sources, the diffuse ISM, etc., and has a highly interesting potential <strong>for</strong> serendipity<br />
discoveries. Complementary HST/ACS multicolour imaging <strong>for</strong> the obvious target, the 1000<br />
nearest star <strong>for</strong>ming high-inclination galaxies, is being obtained as part of the Smartt-Gilmore<br />
Supernova Progenitor program, as is much direct VLT imaging. We will of course have VST<br />
and VISTA imaging available on the same time scales.<br />
Note also that qualitatively the survey will be superior to any other ground-based survey of<br />
nearby galaxies, since it provides the advantage of high spatial contrast source discrimination<br />
(“crowded field 3D spectroscopy”, see above), and an order of magnitude higher spectral<br />
contrast than typical narrow-band imaging surveys.<br />
The combination of large field-of-view with seeing-limited spatial sampling (WFM) makes<br />
MUSE an unrivalled tool <strong>for</strong> background-limited spectroscopy of resolved stellar populations<br />
in nearby galaxies: 260× more efficient than FLAMES, and 210× more efficient than the<br />
GMOS-IFU.<br />
4.4.1. Stellar evolution of the most massive stars<br />
How the most massive stars evolve from the main-sequence and produce populations of blue<br />
and red supergiants, luminous blue variables, Wolf-Rayet stars, and finally the core-collapse<br />
supernovae Types II, Ib and Ic is not well understood. The initial metallicity of the stars is a<br />
key ingredient, and will affect star <strong>for</strong>mation, mass-loss rates, rotation and overall evolution.<br />
We need to go beyond the Magellanic Clouds (0.5Z <br />
and 0.2Z <br />
) to probe extreme systems.<br />
Massive star evolutionary phases last a very short time and one must expend a lot of telescope
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time to spectroscopically observe every luminous star in a star-<strong>for</strong>ming region. Because these<br />
regions are generally crowded, this has not been done with conventional spectrographs in<br />
single or multi-slit mode. Integral field spectroscopy with AO correction is the ideal approach<br />
to ensure completeness.<br />
Extensive work is underway with the VLT on identified single stars, using FLAMES. Much<br />
HST imaging is underway. However, all this, while valuable, essentially assumes that<br />
interesting sources are already known: in fact, the bolometric correction <strong>for</strong> very hot sources<br />
is such they are not ab initio knowable: complete spectroscopic surveys of star <strong>for</strong>ming<br />
regions are essential <strong>for</strong> reliable analyses.<br />
Fig. 4-10: Examples of southern nearby disk galaxies, suitable <strong>for</strong> a census of massive stars: NGC45,<br />
NGC55, NGC247, NGC253, NGC300, NGC7793 (left-right, top-bottom). The DSS frames subtend a FOV<br />
of 5x5arcmin 2 .<br />
Massive stars play a key role in the chemical enrichment of galaxies as well as in the<br />
dynamics of the interstellar medium by their large input of momentum and kinetic energy and<br />
their radiative luminosity. The understanding of the evolution of galaxies depends on our<br />
knowledge and understanding of the evolution of massive stars. Un<strong>for</strong>tunately, this evolution<br />
is not well known. We roughly understand the overall trends and sequences from evolutionary<br />
calculations (e.g. Maeder et al. 1991, Meynet& Maeder, 2000), but the observations show<br />
several classes of massive stars that do not properly fit into these evolutionary schemes. The<br />
goal is to unravel the evolution of massive stars by observing and studying large numbers of<br />
massive stars, and fitting them into evolutionary schemes by using new state-of-the-art<br />
evolutionary calculations, including rotation.<br />
Several classes of massive stars are known:<br />
• the luminous O and B stars
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• the Luminous Blue Variables (LBVs) with their large variability on many timescales<br />
• the B-type hypergiants which have spectra identical to those of LBVs, but do not<br />
show the large variability<br />
• the B[e]-supergiants with their outflowing disks<br />
• the WN/Ofpe stars with their strong emission lines<br />
• the Wolf Rayet stars with their N-rich (WN), C-rich (WC) or O-rich (WO) spectra.<br />
• t<strong>here</strong> are peculiar massive binary objects with relativistic stars and accretion disks, e.g.<br />
SS433 and Cyg X-3. All these classes of stars show emission lines in their optical<br />
spectrum.<br />
It is generally accepted that the evolution starts with “normal” O and B stars in the main<br />
sequence phase and ends with the Wolf-Rayet (WR) phase, be<strong>for</strong>e the stars explode as<br />
supernovae (e.g. Maeder and Conti, 1994; Lamers et al. 1991). However, it is not clear how<br />
and w<strong>here</strong> other observed classes of massive stars fit in the evolutionary scheme: H-rich WN<br />
stars, LBVs, hypergiants, B[e]-supergiants, Ofpe/WNL stars. Studies of massive stars in the<br />
Milky Way have not provided a conclusive picture <strong>for</strong> the problem since extinction in the<br />
galactic plane prevents systematic studies of sufficent numbers of stars of these different<br />
classes. For instance, only five confirmed LBVs have been found in our Galaxy (Humphreys<br />
and Davidson, 1994) and only two confirmed B[e]-stars (Lamers et al. 1998). In addition, the<br />
distances and hence the luminosities of the massive stars in our Galaxy are not always known<br />
with sufficient accuracy to compare different types of stars. The study of the LMC and SMC<br />
provides a view with little extinction of stars at the same distance. However, t<strong>here</strong> the<br />
numbers of massive stars is small, except in the very young 30 Doradus region, which<br />
contains no LBVs and B[e]-stars yet.<br />
Objectives:<br />
The immediate goal is the discovery and systematic study of a large number of H α emitting<br />
stars with 3D spectroscopy, in typically 5x5 arcmin 2 fields of nearby southern disk galaxies,<br />
i.e. the Sculptor Group galaxies NGC55, NGC247, NGC300, etc. The final aim is to unravel<br />
the evolution of massive stars, by means of a careful study of the properties, interrelations and<br />
relative numbers of different classes of massive stars and comparing these with new stellar<br />
evolution calculations. The study combines the very powerful method of 3D spectroscopy<br />
with deep photometry and high resolution HST direct imaging.<br />
Feasibility:<br />
A table of signal-to-noise estimates <strong>for</strong> a range of typical massive stars at a distance of m-M =<br />
26.53 (Fornax group, Freedman et al. 2001) obtained with total exposure times of 4 hours and<br />
1 hour per field, respectively, is listed below. The corresponding absolute visual magnitudes<br />
<strong>for</strong> this distance are also listed in the last column.
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Tab. 4-1 S/N estimates at 5500 Å <strong>for</strong> different exposure times, R=2000<br />
M V<br />
V Exposure [sec] S/N<br />
d=2Mpc<br />
20.7 4x 3600 100 -5.83<br />
21.9 4x 3600 50 -4.63<br />
23.9 4x 3600 10 -2.63<br />
19.3 1x 3600 100 -7.23<br />
23.2 1x 3600 10 -3.33<br />
@<br />
Tab. 4-2 shows <strong>for</strong> different masses of 20 … 120 M ◉ the evolution of spectral type and<br />
absolute visual magnitude MV with age (adopted from Massey 2003). At the distance of<br />
Fornax, the stars <strong>for</strong> which deep 4 hour exposures will yield high S/N (~100) are shown in<br />
orange, medium S/N (~50) in yellow, and low S/N (~10) in beige.<br />
120 M ◉<br />
85 M ◉<br />
60 M ◉<br />
40 M ◉<br />
25 M ◉<br />
20 M ◉<br />
Tab. 4-2<br />
0.0<br />
Myr<br />
-6.2<br />
O3 V<br />
-5.7<br />
O3 V<br />
-5.2<br />
O4 V<br />
0.0<br />
Myr<br />
-4.6<br />
O6 V<br />
-3.8<br />
O8 V<br />
-3.5<br />
O9.5 V<br />
0.5<br />
Myr<br />
Evolution of massive stars at galactic metallicity<br />
1.0 1.5 2.0 2.5 3.0<br />
Myr Myr Myr Myr Myr<br />
-6.9<br />
-6.6<br />
-7.0 -8.6<br />
O5.5<br />
O4 III O5 If WNL<br />
III<br />
-6.4<br />
O3 V<br />
-5.9<br />
O4 V<br />
-5.4<br />
O5 V<br />
1.0<br />
Myr<br />
-4.8<br />
O6.5 V<br />
-4.0<br />
O8 V<br />
-6.1<br />
O4 III<br />
-5.5<br />
O5 V<br />
2.0<br />
Myr<br />
-5.1<br />
O7 III<br />
-4.1<br />
O9 V<br />
-3.7<br />
O9.5 V<br />
-6.4<br />
O5.5<br />
III<br />
-5.7<br />
O5.5<br />
III<br />
3.0<br />
Myr<br />
-5.5<br />
O8 III<br />
-4.3<br />
O9 V<br />
-6.9<br />
O7 If<br />
-5.9<br />
O6.5<br />
III<br />
4.0<br />
Myr<br />
-6.6<br />
B0.5 I<br />
-4.6<br />
O9.5<br />
III<br />
-4.0<br />
B0 V<br />
-7.9<br />
B0 I<br />
-5.9<br />
O6.5<br />
III<br />
5.0<br />
Myr<br />
-4.9<br />
O9.5<br />
III<br />
-6.3<br />
O7.5 If<br />
6.0<br />
Myr<br />
-5.6<br />
B0.5 I<br />
-4.4<br />
BO III<br />
-7.2<br />
B0 I<br />
8.0<br />
Myr<br />
-5.3<br />
B1 I<br />
As can be seen in Tab.4-2, all of the rare high mass stars can be observed with very good S/N,<br />
allowing <strong>for</strong> quantitative spectroscopic analysis. In the mass range of 20-25 M◉, supergiants<br />
are observable with good to very good S/N. Wolf-Rayet stars typically have absolute visual<br />
magnitudes of about M V = -4.0, with WN stars covering a larger range of ~-2.5 … -7 (Massey<br />
2003). The detection limit <strong>for</strong> the purpose of classification is nevertheless fainter than this,<br />
since the essential criterion is the presence and strength of emission lines: He II 4686 (WN),<br />
and CIII 4650 (WC). Owing to the comparatively high spectral resolution, MUSE<br />
observations will have a clear advantage over conventional direct imaging searches,
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employing normally filter bandwidths of ~30 Å, which is an order of magnitude larger than<br />
the effective bandwidth of a monochromatic map from a MUSE datacube.<br />
Most WR stars outside the Galaxy have been found in the LMC (134), but only 8 in the SMC,<br />
and further 141 stars in M33, 48 in M31, 4 in NGC6822, 1 in IC1613, and 26 in IC10 (see<br />
review by Massey 2003 and references t<strong>here</strong>in). Typical surface densities are ranging from<br />
~0.7 kpc -2 up to 10-40 kpc -2 , depending on star <strong>for</strong>mation activity and metallicity. The<br />
proposed deep mosaic survey of the southern galaxies NGC45, NGC300, NGC7793, etc. will<br />
result in a number of massive star detections on the order of 1000 per galaxy, and <strong>for</strong> the first<br />
time provide a statistically significant inventory, which presently does not exist because of the<br />
small number of known objects. The existence of such a statistical meaningful database is a<br />
prerequisite be<strong>for</strong>e any break-through in the quantitative description of stellar evolution of<br />
massive stars can be expected ⎯ with important consequences <strong>for</strong> the input physics of<br />
models like Starburst99 <strong>for</strong> use in extragalactic astronomy (Leit<strong>here</strong>r et al. 1999, Smith et al.<br />
2002).<br />
It has recently been shown that the intrinsic luminosity of a massive blue supergiant star is<br />
closely correlated with its wind-momentum. This is termed the Wind Momentum –<br />
Luminosity Relation (WLR), and will potentially allow independent distance moduli to be<br />
obtained to an accuracy of ~10% to spiral galaxies within 10-15Mpc. (Kudritzki et al. 1999,<br />
Smartt et al., 2001, Bresolin et al. 2001). MUSE in its highest spectral resolution mode,<br />
together with AO correction will provide an unprecedented advantage over conventional<br />
spectrographs.<br />
T<strong>here</strong> are a number of galaxies within the Local Group that have massive stellar populations<br />
at very low metallicities, providing close comparison to star <strong>for</strong>mation in the early Universe.<br />
For example GR8, LeoA, SexA, have metallicities ~0.03Z <br />
and probing the massive star<br />
content would give better abundances ratios, complete IMF and star counts in evolutionary<br />
phases, and allow mass-loss to be determined at extremely low metallicities. IFU plus AO<br />
correction would be an ideal, and unique approach.<br />
The evolved descendents of massive O-type main-sequence stars (M <br />
≥ 20M <br />
) include the B,<br />
A and F-type supergiants which are the visually brightest, stable stars in the Universe. Unified<br />
model atmosp<strong>here</strong> theory allows abundances of C, N, O, Mg, Na, Si, S, Al, Ti, Fe, Cr, Sr, Zr.<br />
to be measured in their atmosp<strong>here</strong>s. Crucially they probe the iron-peak elements, allowing<br />
determination of the α/Fe ratio, which is a key probe of galactic chemical evolution.<br />
Observations of these stars together with spectral synthesis will constrain galaxy evolution.<br />
4.4.2. Planetary Nebulae<br />
Extragalactic planetary nebulae (PNe) have been shown to possess unique potential <strong>for</strong> the<br />
study of the star <strong>for</strong>mation history and chemical evolution of galaxies, based on the analysis<br />
of individual objects (Dopita 1997, Richer et al. 1999, Jacoby&Ciardullo 1999). They are<br />
particularly suitable to measure abundance gradients in elliptical galaxies w<strong>here</strong> massive stars<br />
or H II regions cannot be used. Coupled with radial velocities which are easily measured from<br />
the bright [O III] 5007 line, PNe provide an ideal tool to investigate the merger history of<br />
NGC5128, w<strong>here</strong> a total of 1140 PNe have been discovered to date. While conventional MOS
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instruments at 8m class telescopes are most efficiently used to measure the halo PNe, this<br />
technique fails completely in the high surface brightness regions near the nucleus (Walsh et<br />
al. 1999). Crowded Field 3D Spectroscopy is the only method to provide the required<br />
accuracy <strong>for</strong> background subtraction in this galaxy. The combination of high spatial<br />
resolution, 1’ FOV, large wavelength coverage, a suitable spectral resolution (R~1500) and<br />
high efficiency will make MUSE an unchallenged instrument <strong>for</strong> these observations.<br />
Fig. 4-11: Planetary Nebulae in NGC300, discovered with [O III] onband/offband imaging technique,<br />
using SUSI at the NTT. The frame in the color composite picture of the galaxy indicates the 2.2x2.2 arcmin 2<br />
FOV of the CCD camera. [O III] onband (top) and offband (bottom) frames are shown to the right. Several<br />
examples of XPN are indicated in the onband image (left to right): objects #27 (26.07), #23 (25.69), #2<br />
(23.00), #7 (23.25), #13 (24.38). From Soffner et al. 1996, m 5007 magnitudes in paranthesis. The total<br />
exposure time of the onband frame is 1800 sec<br />
XPN are ideal tracers of intermediate age and old extragalactic stellar populations, because<br />
their hot central stars are among the most luminous stars in the HRD, emitting their radiation<br />
predominantly in the UV. A substantial fraction (of order 10%) of the total luminosity is reemitted<br />
by the surrounding nebula in a prominent emission line spectrum, which gives enough<br />
contrast (<strong>for</strong> the bright lines) to detect the object as a point source against the bright<br />
background of unresolved stars of the parent galaxy. A practical application of this property<br />
has consisted in narrow-band imaging spectrophotometry, centered on the bright emission line<br />
of [O III] λ5007, and the construction of PN luminosity functions (PNLF) <strong>for</strong> the purpose of<br />
distance determinations (see review by Ciardullo 2003). Approximately 5000 XPN in more<br />
than 40 galaxies have been identified to date (Ford et al. 2002).<br />
Currently the only way to measure individual abundances from old or intermediate age stars<br />
in galaxies more distant than the Magellanic Clouds is through the emission line spectra of<br />
extragalactic planetary nebulae (Walsh et al. 2000). This approach has some similarities with<br />
the standard method of measuring abundance gradients from individual H II regions in the<br />
disk of spiral galaxies (Shaver et al. 1983, Zaritsky et al. 1994). As opposed to H II regions,<br />
XPN metallicities can be derived in a homogeneous way <strong>for</strong> galaxies of any Hubble type, and
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on all scales of galactocentric distances. The task of obtaining abundance gradients out to<br />
large radii, w<strong>here</strong> a low surface-brightness precludes to measure reliable colors or absorption<br />
line indices, can be addressed with XPN, providing important constraints <strong>for</strong> galactic<br />
evolution models (Worthey 1999). Moreover, since radial velocities of XPN are measurable<br />
out to several effective radii, they are potentially useful <strong>for</strong> probing the gravitational potential<br />
of galaxies (Méndez et al. 2001, Romanowsky et al. 2003), and <strong>for</strong> tracing merger events (Hui<br />
et al. 1995, Durrell et al. 2003, Merrett et al. 2003).<br />
Recently, XPN and an H II region have been detected in the intracluster space of the Virgo<br />
cluster, giving an excellent opportunity to study the properties of this unique stellar<br />
population and, potentially, their star <strong>for</strong>mation history and metallicity (Arnaboldi et al. 2002,<br />
Gerhard et al. 2002, Feldmeier et al. 2003).<br />
Several authors have pioneered spectroscopic observations of individual XPN in nearby<br />
galaxies and derived abundances from the observed emission line intensities, e.g. Jacoby &<br />
Ciardullo 1999 (M31), Richer et al. 1999 (M31, M32), Walsh et al. 1999 (NGC5128),<br />
Magrini et al. 2003 (M33). A wealth of data exists <strong>for</strong> Magellanic Cloud objects which are an<br />
order of magnitude closer and t<strong>here</strong><strong>for</strong>e much easier to observe than those in M31 and other<br />
more distant galaxies. The LMC study of Dopita et al. 1987 has demonstrated the potential of<br />
XPN to investigate the chemical evolution of stellar populations.<br />
Un<strong>for</strong>tunately, the study of XPN near the center of the more distant galaxies is complicated<br />
by source confusion, either from the continuum light of unresolved stars with a small angular<br />
separation from the target, or from the emission line spectra of H II regions and diffuse<br />
nebulosities of the interstellar medium (ISM), or from both components at the same time. In<br />
fact, these first studies were all significantly affected by background contamination, which is<br />
a severe problem in particular <strong>for</strong> the faint nebular diagnostic lines. Roth et al. 2003 presented<br />
a methodological study of selected XPN in the bulge of M31, showing that 3D spectroscopy<br />
is an ideal technique to overcome these difficulties.<br />
Objectives:<br />
The immediate goal is to per<strong>for</strong>m deep 3D spectrophotometry of XPN in early and late type<br />
galaxies, from relatively nearby objects (~3 Mpc) out to Virgo. From the comparison of the<br />
observed emission line intensities with ionization models, it will be possible to derive nebular<br />
abundances of He, N,O, Ne, S, Ar, and to constrain central star properties (effective<br />
temperature, mass). Radial velocities are easily measurable from the bright [O III] λ5007 line.<br />
The final objective is to provide independent kinematic and abundance in<strong>for</strong>mation <strong>for</strong> the<br />
intermediate/old parent populations, complementing photometric and integrated light stellar<br />
population studies, and new data coming from quantitative spectroscopy of individually<br />
resolved, massive stars. As an asset, the analysis will map the extinction over the face of the<br />
galaxies under study.<br />
Feasability:<br />
Planetary nebulae span a wide range of apparent brightness in their prominent [O III]<br />
emission line λ5007. Narrow-band imaging observations of numerous galaxies, beginning<br />
with the pioneering work of Jacoby 1989 and Ciardullo et al. 1989, have established an<br />
invariable shape of the PNLF, with a cutoff magnitude of M5007 = –4.5, w<strong>here</strong> m 5007 = -2.5
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log F(λ5007) –13.74. For example, Soffner et al. (1996) discovered 34 PNe in NGC300,<br />
using the NTT + SUSI (2.2x2.2 arcmin 2 FOV) under less than ideal observing conditions<br />
(seeing 2.0”-0.9”), and with exposure times of 3600s per field, <strong>for</strong> three fields centered on the<br />
nucleus. The magnitude range of these objects is m 5007 = 22.85–27.08, corresponding to flux<br />
levels of 2.4x10 -15 – 5x10 -17 erg/cm 2 /sec, respectively.<br />
First of all, using the light collecting power of the VLT and excellent seeing conditions, the<br />
detection limit with MUSE will be 2 magnitudes fainter than this. Due to the 10-fold smaller<br />
bandwidth of a MUSE exposure, compared with a the typical filter bandwidth of PNLF<br />
observations, the <strong>for</strong>mer has a significant advantage over the latter in terms of backgroundlimited<br />
exposures in high surface brightness regions near the nucleus, w<strong>here</strong> normally<br />
narrow-band imaging data tend to become incomplete. Using 3D spectroscopy as an<br />
extremely narrow-bandwidth filter, MUSE will detect hundreds of PNe two orders of<br />
magnitudes further down the PNLF, compared to the earlier NTT observations.<br />
Secondly, spectrophotometry of the PN emission line spectrum will be feasible <strong>for</strong> the entire<br />
range of magnitudes m 5007 = 22.85 … 27.08, even <strong>for</strong> the faint diagnostic lines, whose line<br />
intensities are typically no brighter than 10 -2 I([O III]).<br />
Tab. 4-3 S/N estimates <strong>for</strong> PNe at [O III] 5007 Å<br />
Flux<br />
(erg/cm 2 /sec)<br />
Exposure [sec] S/N<br />
5x10 -17 4x 3600 100<br />
5x10 -18 4x 3600 21<br />
5x10 -19 4x 3600 3<br />
The unique contribution of MUSE in all these case is the combination of area and an ability to<br />
exploit enhanced seeing. All these objects are `crowded’ under normal conditions, making<br />
impossible a quantitative study of the astrophysics. For example, the astrophysics of our<br />
Galactic nucleus was unknown until the high resolution studies by Genzel’s group. With<br />
supernova progenitors, only one sound precursor identification was available until very<br />
recently. Similar advances may confidently be expected in all the fields of star <strong>for</strong>mation,<br />
high-mass stars, mass loss, dense dynamical systems, resolved emission line sources (PNae,<br />
SNae, jets, etc) and so on, when data become available from MUSE.<br />
References<br />
Alves & Nelson, 2000, ApJ, 542, 789<br />
Arnaboldi, M.et al. 2002, AJ 123, 760<br />
Bresolin, F., Kudritzki, R. P., Méndez, R. H., Przybilla, N. 2001, ApJ 548, L159<br />
Becker, T., Fabrika, S., Roth, M.M. 2003, AN (accepted), astro-ph/0311315<br />
Ciardullo, R., Jacoby, G.H., Ford, H.C., Neill, J.D. 1989, ApJ 339, 53<br />
Ciardullo, R. 2003, in Workshop on "Stellar Candles <strong>for</strong> the Extragalactic Distance Scale",<br />
held in Concepcion, Chile, astro-ph/0301279<br />
Dopita, M. A. et al. 1997, ApJ 474, 188<br />
Durrell, P.R., Mihos, J.C., Feldmeier, J.J., Jacoby, G.H., Ciardullo, R. 2003, ApJ 582, 170<br />
Elson et al. 1997, MNRAS 289, 157<br />
Feldmeier, J.J. Ciardullo, R., Jacoby, G.H., Durrell, P.R. 2003, ApJS 145, 65
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Reference: MUSE-MEM-SCI-052<br />
Issue: 1.3<br />
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Ford, H., Peng, E., Freeman, K. 2002, in “The Dynamics, Structure & History of Galaxies”,<br />
ASP Conf. Proc. Vol. 273, eds. G.S. Da Costa and H. Jerjen, p.41<br />
Freedman, W. et al. 2001, ApJ 553, 47<br />
Gerhard, O., Arnaboldi, M., Freeman, K.~C., & Okamura, S.\ 2002, ApJ 580, L121<br />
Hawarden, T.G., Dravins, D., Gilmore, G.F., Gilmozzi, R., Hainaut, O., Kuijken, K.,<br />
Leibundgut, B., Merrifield, M.R., Queloz, D., Wyse, R.F.G. 2003, SPIE4840, p. 299<br />
Hui, X., Ford, H. C., Freeman, K. C., Dopita, M. A. 1995, ApJ 449, 592<br />
Humphreys, R. Davidson, K., 1994, RASP, 106, 1025<br />
Jacoby, G.H. 1989, ApJ 339, 39<br />
Jacoby, G. H., Ciardullo, R. 1999, ApJ 515, 169<br />
Kudritzki R.P. 1998, in “Stellar Astrophysics <strong>for</strong> the Local Group.” 8th Canary Island Winter<br />
School, eds. A.Aparicio, A.Herrero, F.,Sanchez, New York, Cambridge Univ. Press., p.149<br />
Lamers H.J.G.L.M. et al., 1991, ApJ 368, 538<br />
Lamers H.J.G.L.M. et al., 1998, A&A v.340, 117<br />
Leit<strong>here</strong>r, C. et al. 1999, ApJS 123, 3<br />
Maeder A. et al., 1991 A&A, 242, 93<br />
Maeder, A. and Conti, P.S. 1994, ARAA, 32, 227<br />
Magrini, L., Perinotto, M., Corradi, R. L. M., Mampaso, A. 2003, A&A 400, 511<br />
van der Marel et al., 2002, AJ, 124, 2639<br />
Massey, P. 2003, Ann. Rev. Astron. Astrophys. Vol 41, 15<br />
Massey, 2002, ApJSS, 141, 81<br />
Mateo, M. 1998, in “Stellar Astrophysics <strong>for</strong> the Local Group.” 8th Canary Island Winter<br />
School, eds. A.Aparicio, A.Herrero, F.,Sanchez, New York, Cambridge Univ. Press., p.407<br />
Maund, J, etal Science Jan 24 2004<br />
Méndez, R.H et al. 2001, ApJ 563, 135<br />
Mehlert, D., Saglia, R. P., Bender, R., Wegner, G. 2000, A&A 141, 449<br />
Merrett, H.R. et al. 2003, MNRAS Letters (accepted), astro-ph/0311090<br />
Meynet, G. and Maeder, A., 2000, A&A, 361, 101<br />
Monteverde, M. I., Herrero, A., Lennon, D. J., Kudritzki, R.-P. 1997, ApJ 474, L107<br />
Najita, J., Strom, S.E. 2002, SPIE 4835, 1<br />
Richer, M. G., Stasi\'nska, G., McCall, M. L. 1999, A&AS 135, 203<br />
Romanowsky, A.J. et al. 2003, Science, Vol.301, No.5640, 1696<br />
Roth, M.M., Becker, T., Kelz, A., Schmoll, J. 2003, ApJ (accepted), astro-ph/0311407<br />
Shaver, P. A., McGee, R. X., Netwon, L. M., Danks, A. C., Pottasch, S. R. 1983, MNRAS 204,<br />
53<br />
Smartt, S. J., Crowther, P. A., Dufton, P. L., Lennon, D. J., Kudritzki, R. P., Herrero,A.,<br />
McCarthy, J. K., Bresolin, F. 2001, MNRAS 325, 257<br />
Smecker-Hane T. A., Cole A. A., Galagher III J. S., Stetson P. B., 2002, ApJ, 566, 239<br />
Smith, L.J., Norris, R.P.F., Crowther, P. 2002, MNRAS 337, 1309<br />
Soffner, T., Méndez, R.H., Jacoby, G.H., Ciardullo, R., Roth, M.M., Kudritzki, R.P. 1996,<br />
A&A 306, 9<br />
Urbaneja, M.A., Herrero, A., Bresolin, F., Kudritzki, R.-P., Gieren, W., Puls, J. 2003, ApJ<br />
584, L73<br />
Venn, K., McCarthy, J.K., Lennon, D.J., Pryzbilla, N., Kudritzki, Lemke, M. 2000, ApJ 541,<br />
610<br />
Venn, K. A., Lennon, D. J., Kaufer, A., McCarthy, J. K., Pryzbilla, N., Kudritzki, R., P.,<br />
Lemke, M., Skillman, E. D., Smartt, S. J. 2001, \apj 547, 765
Title: Science Case<br />
Reference: MUSE-MEM-SCI-052<br />
Issue: 1.3<br />
Date: 04/02/2004<br />
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Walsh, J. R., Walton, N.A., Jacoby, G. H., Peletier, R.F. 1999, A&A 346, 753<br />
Walsh, J.R., Jacoby, G.H., Peletier, R.F., Walton, N.A. 2000, SPIE 4005, p.131<br />
Worthey, G., in “Chemical Evolution from Zero to High Redshift”, eds. J. R. Walsh, M. R.<br />
Rosa,Springer, Heidelberg, p.168<br />
Wyse, R.F.G., Olsen, K., Rich, M., O'Connell, R. 2000, in The GSMT Book: Report of the<br />
Stellar Populations Panel, http://www.aura-nio.noao.edu/book/index.html<br />
Zaritsky, D., Kennicutt, R.C., Huchra, J.~P. 1994, ApJ, 420, 87
5. Solar system<br />
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5.1. Introduction<br />
T<strong>here</strong> are a number of exciting scientific questions in the field of planetary sciences to which<br />
MUSE will significantly contribute. We consider 3 major distinct categories:<br />
• Investigation of the planetary surfaces of the Galilean satellites and of Titan's<br />
atmosp<strong>here</strong> and surface,<br />
• Study and mapping of the optical and mineralogical surface heterogeneities of the<br />
small bodies of the solar system (earth-grazing and main belt asteroids, comets),<br />
• Monitoring of the temporal evolution (e.g. seasonal effects) of the atmosp<strong>here</strong>s of the<br />
giant planets and their dynamics, with special emphasis on the observation of the<br />
atmosp<strong>here</strong>s of Neptune and Uranus.<br />
5.2. Galilean Satellites and Titan surfaces<br />
As recently explored by the Galileo mission and AO-assisted ground-based telescopes, the<br />
surfaces of the Galilean satellites are undergoing major resurfacing processes as the result of<br />
different geological processes. Intensive volcanic resurfacing on a planetary scale is occurring<br />
on Io, as evidenced by the significant regional surface changes observed in the hot spots areas<br />
between the Voyager and Galileo missions (Spencer et al., 1996; McEwen et al., 1998;<br />
McEwen et al., 2000; Douté et al., 2001; Geissler et al., 2001; Marchis et al., 2002). It can be<br />
traced and documented spectroscopically in the visible-near infrared range, with special<br />
emphasis on the surface mixing related to the occurrence of SO 2 species. MUSE could carry<br />
out observations aimed at:<br />
• Providing a global spectroscopic imaging coverage, including the edge of the 1 micron<br />
domain which is sensitive to the presence of mafic silicates, thus determining the<br />
proportion of the surface covered by exposed silicate magma;<br />
• Monitoring through time major surface changes occurring on Io beyond 2011 (i.e. 5 to<br />
10 years after the Galileo mission) and consequently to constrain the amount of<br />
volcanic resurfacing at planetary scale (see Fig. 5-1).<br />
“High angular resolution provided by adaptive optics systems on 8 m class telescopes is a<br />
promising tool <strong>for</strong> monitoring the volcanic activity of Io from the ground with a spatial<br />
resolution better than the global Galileo/NIMS observations. With the end of the Galileo<br />
mission, the future monitoring of Io’s volcanism lies in the hands of terrestrial observers with<br />
the ability to make spectroscopic AO observations" (Marchis et al., 2002). MUSE will play a<br />
key role in fulfilling this responsibility of ground-based observers to monitor activity on IO,<br />
providing unique access to high spatial resolution spectroscopic imaging at visible and nearinfrared<br />
wavelengths in the post-Galileo mission era.
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Fig 5-1 - Taken from Marchis et al., 2002). It demonstrates what could be monitored at Io by MUSE in<br />
the visible-nIR domain. (a) Jupiter-facing hemisp<strong>here</strong> observed with the Keck AO system. The basicprocessed<br />
images from 20 February 2001 (first row) are displayed. The second row corresponds to the<br />
same images after applying the MISTRAL deconvolution process. Albedo features, similar to the 20-kmresolution<br />
reconstructed GALILEO/SSI image (right column) are easily detected. The last row shows the<br />
22 February 2001 images, which are dominated by the presence of the Surt outburst. (b) Observations<br />
from 19 February 2001. Two hot spots, corresponding to Tvashtar (North) and Amirani, are clearly<br />
detected in the H and K bands. Note the bad quality of the J-band image after deconvolution, due to the<br />
poor seeing condition of this observing night.
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For Europa, Ganymede and Callisto, more subtle resurfacing processes are now also<br />
recognized and an intermittent systematic monitoring of the optical surface properties should<br />
also be made. All these objects have an apparent diameter ranging between 1 and 2", and are<br />
t<strong>here</strong><strong>for</strong>e perfectly suited to the MUSE-HR field of view, allowing efficient surveying and<br />
monitoring of their surfaces.<br />
MUSE could also extend the spectro-imaging monitoring of Titan's atmosp<strong>here</strong> to be<br />
conducted by Cassini during the period 2004-2007 and which is also of high scientific value<br />
and benefit. This would significantly contribute to the understanding of the general<br />
atmospheric circulation <strong>for</strong> which the present modelling ef<strong>for</strong>ts are only considering a<br />
standard atmospheric photochemistry profile, with no lateral or temporal variations. At<br />
present, such modelling simulates latitudinal temperature contrasts in the stratosp<strong>here</strong> that are<br />
significantly weaker than those observed by Voyager 1, and it may be partly due to the<br />
absence of the spatial and temporal variations of the abundances of molecular species and<br />
haze.<br />
By considering different spectral windows within the visible to near-infrared wavelength<br />
range of a single MUSE exposure, it will be possible to probe down into the atmosp<strong>here</strong> of<br />
Titan, and measure the mesoscale lateral and vertical structures and characteristics. Methane<br />
and absorption bands have been documented by earth-based spectroscopic observations in the<br />
4900-5500; 6000-6600; 8700-9300 Å domains (Moreno et al., 1991, Coustenis et al., 1995;<br />
Combes et al., 1997) and the comparison of spectral images acquired by the WFPC camera of<br />
Hubble Space Telescope at 4400, 5500 and 8890 Å with Voyager images indicate<br />
atmospheric seasonal changes (Caldwell et al., 1992; Smith et al., 1996). Temporally-resolved<br />
monitoring of Titan would be well-suited to MUSE's high-resolution capabilities, with the<br />
diameter of Titan (including its atmosp<strong>here</strong>) being in the range of 1.0-1.2", resulting in a<br />
predicted effective spatial resolution of 140-150 km per lens.<br />
5.3. Surface heterogeneities of the small bodies<br />
For the study of comets and asteroids in the solar system, MUSE will produce several<br />
major breakthroughs. For the study of comets, t<strong>here</strong> will be:<br />
- Study at high spatial resolution (3.5km/pixel <strong>for</strong> a comet at 0.2 a.u.) of morphology of<br />
the internal coma, within 300-500 km around the cometary nucleus, of the<br />
relationships with the activity of the nucleus (e.g., distribution of active zones and the<br />
rotational parameters of the nucleus).<br />
- Spectroscopic study of the cometary dust: spectral variations as a function of the<br />
distance to the nucleus. Relationships with the ejected gases.<br />
- In a few cases (closest approaches), it might be possible to extract the contribution of<br />
the nucleus to the reflected light by the centre of the coma and consequently to<br />
estimate the diameter of the nucleus.<br />
and <strong>for</strong> asteroids:<br />
- Despite the recent extension toward the infrared, the general taxonomic classes of<br />
asteroids are based on colour photometry in the 0.3-1.1 micron domain (see summary<br />
of Tholen and Barucci, 1989).
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- The asteroids orbiting the sun within the main belt have perihelion distances ranging<br />
between 1.6 and 3.3 a.u.. The possible spatial resolutions, assuming an angular<br />
resolution of 0.025", would thus range from 10 to 40 km/pixel.<br />
- For the largest objects (more than 10), it permits the mapping of the optical and<br />
mineralogical surface heterogeneities and consequently provides insight into their<br />
accretional and subsequent geochemical differentiation history. As an example, taking<br />
advantage of its rotation, MUSE could produce a global map of Ceres (diameter: 1025<br />
km).<br />
5.4. Temporal changes in Jupiter, Saturn, Uranus and<br />
Neptune<br />
The predicted spatial resolution delivered by MUSE in the high-resolution mode<br />
(corresponding to a 0.025" angular resolution) translates into effective physical scales as<br />
follows: 75 km/pixel at the distance of Jupiter, 150 km at Saturn, 300 km at Uranus and 500<br />
km at Neptune. The latter two objects represent the best candidates <strong>for</strong> both a synoptic survey<br />
and a truly new return in terms of scientific knowledge. Furthermore, their apparent diameters<br />
of about 4" and 2.3", respectively, make them ideal <strong>for</strong> global monitoring given the field of<br />
view of MUSE in its high spatial resolution mode. For Jupiter and Saturn, a global monitoring<br />
would be more time-consuming, requiring mosaics of several high-resolution fields. Instead,<br />
it may be more practical <strong>for</strong> these objects to target regional areas of interest (e.g. the red spot,<br />
polar regions, etc.).<br />
The key contribution of MUSE would be to monitor through time the mesoscale changes in<br />
the atmospheric patterns with the possibility of probing the 3-D atmospheric structure by<br />
examining different spectral windows along the extensive MUSE wavelength range,<br />
depending on the considered spectroscopic absorptions related to gaseous species such as:<br />
CO, C2H2, NH3, HC3N, CH4, etc. (e.g., Tomasko et al., 1984; West et al., 1986). For<br />
instance, in the case of the atmosp<strong>here</strong>s of Uranus and Neptune, photons in the 4900-6600 Å<br />
wavelength range penetrate to the deep convectively mixed atmospheric layers, giving<br />
in<strong>for</strong>mation on the deep methane abundance and aerosols properties (Moreno, et al., 1986).<br />
References:<br />
Caldwell, J., C.C., Cunningham et al. (1992). Titan: Evidence <strong>for</strong> seasonal change- A<br />
comparison of Hubble Space Telescope and Voyager images, Icarus, 96, 1-9.<br />
Combes, M., L. Vapillon, E. Gendron, A. Coustenis, O. Lai, R. Wittemberg, and R.<br />
Sirdey.(1997). Spatially Resolved Images of Titan by Means of Adaptive Optics, Icarus, 129,<br />
482-497<br />
Coustenis,A., E. Lellouch, J. P. Maillard, and C. P. McKay. (1995).Titan's surface:<br />
composition and variability from the near-infrared albedo, Icarus, 118, 87-104.<br />
Doute, S., B. Schmitt, R. Lopes-Gautier, R. Carlson, L. Soderblom, J. Shirley and the Galileo<br />
NIMS Team 2001, Mapping SO2 frost on Io by the modeling of NIMS hyperspectral images.<br />
Icarus 149, 107–132.<br />
Geissler, P., A. McEwen, C. Phillips, D. Simonelli, R.M.C. Lopes, and S. Douté (2001).<br />
Galileo Imaging of SO2 frosts on Io, J.geophys. Res., 106, E12, 33253-266.
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Marchis,F.,I., de Pater, A.G. Davies, H.G. Roe, T. Fusco, D. Le Mignant, P. Descamps, B.A.<br />
Macintosh, and R. Prangé 2002). High-resolution Keck Adaptive Optics Imaging of Violent<br />
Volcanic Activity on Io, Icarus, 160, 124-131.<br />
McEwen, A. S., L. Keszthelyi, P. Geissler, D. P. Simonelli, M. H. Carr, T. V., Johnson, K. P.<br />
Klaasen, H. H. Breneman, T. J. Jones, J. M. Kaufman, K. P., Magee, D. A. Senske, M. J. S.<br />
Belton, and G. Schubert (1998). Active volcanism on Io as seen by Galileo SSI. Icarus 135,<br />
181–219.<br />
McEwen, A. S., M. J. S. Belton, H. H. Breneman, S. A. Fagents, P. Geissler, R. Greeley, J.W.<br />
Head, G. Hoppa,W. L. Jaeger, T. V. Johnson, L. Keszthelyi, K. P. Klaasen, R. Lopes-Gautier,<br />
K. P. Magee, M. P. Milazzo, J. M. Moore, R. T. Pappalardo, C. B. Phillips, J. Radebaugh, G.<br />
Schubert, P. Schuster, D. P. Simonelli, R. Sullivan, P. C. Thomas, E. P. Turtle, and D. A.<br />
Williams (2000). Galileo at Io: Results from high-resolution imaging. Science 288, 1193–<br />
1198.<br />
Moreno, F., A., Molina and J.L. Ortiz (1991). CCD spectroscopic observations of saturn,<br />
Uranus, Neptune, and Titan during the 1990 apparitions, Icarus, 93, 88-95.<br />
Tholen, D.J. and M.A., Barucci (1989). Asteroid taxonomy, In Asteroids II, Eds. R.P. Binzel,<br />
T. Gehrels, and M.S. Matthews, 298-315, Univ. Of Arizona Press, Tucson.<br />
Smith P.H., M. T. Lemmon, R. D. Lorenz, L. A. Sromovsky, J. J. Caldwell, and M. D. Allison<br />
(1996). Titan's Surface, Revealed by HST Imaging, Icarus, 119, 336—34<br />
Spencer, J. R., and N. M. Schneider (1996). Io on the eve of the Galileo mission. Ann. Rev.<br />
Earth Planet Sci., 24, 125-190.
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6. Serendipity<br />
<strong>Astronomy</strong> is to a significant degree still driven by unexpected discovery (e.g. dark matter<br />
and dark energy). These discoveries are often made by pushing the limit of observations with<br />
the most powerful telescopes and/or opening a new area of the instrumental parameter space.<br />
MUSE is designed to push the VLT to its limit and to open a new parameter space area in<br />
sensitivity, spatial resolution, field of view and simultaneous spectral coverage. We are<br />
convinced that it fulfils all the required conditions to have a large potential of discoveries:<br />
• It will be the first spectrograph that could blindly observe a large volume of space (10 4<br />
Mpc in one deep field), without any imaging preselection.<br />
• It will be the first optical AO assisted IFU working at improved spatial resolution (0.3<br />
arcsec FWHM) in most atmospheric conditions (70% probability) with a large sky<br />
coverage (better than 60% at galactic poles).<br />
• It will be the first spectrograph optimized to work with very long integration time (80<br />
hours) and to reach extremely faint emission line detection (3.9 10 -19 erg.s -1 .cm -2 ).<br />
MUSE will thus be able to discover objects<br />
that have measurable emission lines, but<br />
with a continuum that is too faint to be<br />
detected in broad-band imaging. For<br />
example, the deepest broad-band imaging<br />
available today is the HST Ultra Deep Field<br />
(UDF) with I AB 5.5) will have a<br />
continuum bright enough to be detected in<br />
Figure 6-1: Crampton et al. 2002, (astroph/0201344),<br />
Serendipitous discovery of a case of<br />
the UDF. MUSE is also the only instrument<br />
capable of detecting faint diffuse ionized galaxy-galaxy lensing. This geometry allows an<br />
gas, like extended halos or filaments. accurate estimate of the mass distribution of the<br />
Finally, objects with unusual spectral lensing galaxy.<br />
features should also be detected by MUSE,<br />
whatever their broad band magnitude and colours are.<br />
In order to illustrate the enormous scientific multiplex gain from obtaining complete data<br />
cubes over large areas of the sky with wide wavelength (and hence redshift) coverage, we<br />
show in Figure 6-1 an example of galaxy-galaxy lensing discovered during the course of the<br />
Canada-France Redshift Survey (CFRS). In the case of CFRS, two out of 350 galaxies imaged<br />
with HST showed such galaxy-galaxy lensing, so we expect a large number of these in a<br />
MUSE data cube. Galaxy-galaxy lenses are a powerful means of measuring the gravitational<br />
potential of the lensing galaxy.<br />
Serendipity is by essence not easy to quantify and t<strong>here</strong><strong>for</strong>e extremely hard to make a science<br />
case <strong>for</strong>. Despite this, it is very likely that the most memorable results from MUSE will come<br />
from discoveries that are currently not anticipated in this proposal.
7. Instrument requirements<br />
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Instrument requirements are summarized in Table 1. For each science subject we have<br />
identified the following requirements:<br />
• Field of view (FOV) importance (compared to a FOV reduced by a factor 2), quoted<br />
from 1(less important) to 3 (critical)<br />
• AO need, quoted from 0 to 3, with the following meaning:<br />
o 0 : no AO needed<br />
o 1 : AO is preferred but not absolutely requested<br />
o 2 : AO is mandatory to achieve full science but non-AO observations allow<br />
partial fulfilment of the science goals<br />
o 3 : AO is critical to science goals<br />
• Wavelength bandpass. Importance of the bandpass 8 is quoted from 1 (less important)<br />
to 3 (very important). Bandpass are defined according to MUSE spectral range: 0.465-<br />
0.6 µm (B-V), 0.6-0.8 µm (V-I), 0.8-0.96 µm (I-z)<br />
• Importance of R=3000 spectral resolution (compared to R=1500), quoted from 1 (not<br />
important) to 3 (critical)<br />
Science Subject 9<br />
FOV AO Wavelength Spec.<br />
Mode<br />
area<br />
B-V V-I I-z Resol.<br />
Gal. Form SF WFM 3 0 2 2 2 2<br />
Gal. Form MDF WFM 3 1 2 2 3 2<br />
Gal. Form DF WFM 3 3 2 2 3 3<br />
Gal. Form UDF WFM 3 3 2 2 3 3<br />
Near Gal. SBH NFM 1 3 2 1 3 2<br />
Near Gal Kin. & Stel. Gal. WFM 2 2 3 2 1 2<br />
Near Gal Inter. Gal. WFM 3 1 2 2 2 2<br />
Near Gal Star. Form. WFM 2 2 2 3 1 2<br />
Stars YSO WFM 2 2 1 3 1 3<br />
Stars YSO NFM 2 3 1 3 1 3<br />
Stars LMC WFM 3 0 3 2 2 3<br />
Stars Mass. Stars/XPN WFM 3 2 3 2 1 3<br />
Stars Globular cluster WFM 2 3 3 2 2 3<br />
Solar Syst. Planets Atm. NFM 3 3 2 3 1 1<br />
Solar Syst. Satellites/Aster. NFM 3 3 2 2 2 1<br />
Table 1: Main instrument requirement relative to science goals<br />
8 A bandpass is defined as less important if a decrease of 50% in throughput and/or image quality does not affect<br />
science feasibility.<br />
9 SF, MDF, DF and UDF refer to shallow, medium deep, deep and ultra-deep fields. SBH is the supermassive<br />
black hole study, Kin & Stel. Gal. the kinematics and stellar populations in nearby galaxies, Inter. Gal. the<br />
interacting galaxies and Star. Form. the star <strong>for</strong>mation. YSO is the early stage of stellar evolution, LMC the<br />
Large Magellanic Cloud, Mass. Stars/XPN the extragalactic massive stars and planetary nebulae. Planets Atm.<br />
are the planetary atmosp<strong>here</strong> and Aster. the asteroids.
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Note that AO is by definition critical to NFM, whatever the science goals. We now provide<br />
some more detailed comments <strong>for</strong> each science area.<br />
7.1. "Formation of galaxies" science case<br />
For surveys, the field of view is obviously critical. The AO requirements are related to the<br />
depth of the observations. While AO is not necessary <strong>for</strong> the shallow field (SF) and not<br />
mandatory <strong>for</strong> the medium deep field (MDF), it is critical to deep and ultra-deep fields in<br />
view of the limiting flux and spatial resolution goals. The whole MUSE wavelength range is<br />
important: <strong>for</strong> high z galaxies (z>5), the red spectral range is critical, but <strong>for</strong> the cosmic web<br />
measurements (z~3) and spatially resolved spectroscopy (z
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8. Competitiveness<br />
8.1. Introduction<br />
MUSE, as any second generation VLT instrument, should be able to maintain and expand the<br />
VLT world-wide competitiveness in 2010+. As such, it should not only be superior to existing<br />
instruments in terms of per<strong>for</strong>mance, but should also extend the scientific capabilities of the<br />
observatory into unique areas. In this section we try to assess its competitiveness.<br />
Competitiveness is generally a difficult issue to discuss, and even more difficult to properly<br />
quantify. The most valid approach is to compare MUSE with other instruments or facilities in<br />
view of each of the science goals, such as the comparisons already made and discussed<br />
throughout the various science case presentations. The key points to emphasize from these<br />
comparisons are that the MUSE sensitivity per<strong>for</strong>mance is around two orders of magnitude<br />
better than narrow-band imaging; the volume-depth which can be surveyed with MUSE is<br />
unprecedented; and its ability to provide both high-spatial resolution spectroscopic<br />
in<strong>for</strong>mation across a wide field of view, or to get diffraction-limited resolution at visible<br />
wavelengths over a smaller area, are unparalleled by any other instrument, existing or<br />
planned. The MUSE science team believes that the large majority of the presented science<br />
cases are unique to MUSE, either because they are simply not feasible with other instruments<br />
(e.g. detection of high-z faint Ly α emitters that are not detectable in broad band imaging, even<br />
with HST), or because it would take in excess of 10–100 times longer to per<strong>for</strong>m the same<br />
survey with other facilities, and so are simply not tenable. For example, as discussed in<br />
section 4.4, the combination of large field-of-view with seeing-limited spatial sampling makes<br />
MUSE WFM an unrivalled tool <strong>for</strong> background-limited spectroscopy of resolved stellar<br />
populations in nearby galaxies: 260× more efficient than FLAMES, and 210× more efficient<br />
than the GMOS-IFU.<br />
It is also possible to compare MUSE with other instruments in term of generic per<strong>for</strong>mance.<br />
This approach is also important, not only because in seven years, science goals may have<br />
evolved, but also because the science team has its own bias and cannot represent all interests<br />
of the entire ESO community. MUSE is an IFU and should t<strong>here</strong><strong>for</strong>e be compared to others<br />
IFUs that share some of its characteristics: wide-field of view, high spatial resolution, large<br />
simultaneous spectral range and medium spectral resolution. Here we compare the two modes<br />
of MUSE with existing or planned wide-field or high spatial resolution IFUs.
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8.2. Wide field IFU<br />
Among the very few existing wide-field IFUs that could compete with MUSE, VIMOS has<br />
the largest field of view with 0.8 arcmin². This large field of view, however, is only obtained<br />
at R~250: a spectral resolution far too low to be competitive <strong>for</strong> line emission detection and<br />
analysis, or <strong>for</strong> accurate sky-subtraction in the near-infrared. We have t<strong>here</strong><strong>for</strong>e restricted the<br />
comparison to the high spectral resolution mode of VIMOS. To quantify the per<strong>for</strong>mance<br />
comparison between the two instruments, we present in the following table some possible<br />
figures of merit. We have also included SAURON, another wide field IFU operating at the<br />
WHT, as a reference in this table.<br />
SAURON VIMOS MUSE<br />
MUSE/VIMOS<br />
LR mode HR-Blue WFM<br />
Telescope area (m²) 13.1 51.7 51.7 1.0<br />
Ω (arcsec²) 41x33 27x27 60x60 4.9<br />
Grasp (m².arcsec²) 17724 37689 186120 4.9<br />
Throughput 0.2 0.066 0.24 3.6<br />
Etendue 3545 2487 33502 17.6<br />
Resolving power 1200 2500 3000 1.2<br />
Nb of resolved spectral elts 129 920 2048 2.3<br />
Spectral power (x 10 6 ) 0.16 2.3 6.1 2.6<br />
Nb of resolved spatial elts 1,431 1,600 40,000 13.5<br />
Spatial power (x 10 6 ) 1.9 1.2 144.0 120.0<br />
3D power (x 10 12 ) 0.3 2.8 878.4 312.0<br />
Table 8-1: Comparison of wide field IFUS<br />
Note on the table parameters<br />
• Grasp is the field of view times the telescope area<br />
• Etendue is the field of view times the throughput<br />
• Spectral power is the number of resolved spectral elements times the spectral<br />
resolution<br />
• Spatial power is the number of resolved spatial elements times the field of view. In the<br />
case of MUSE, a spatial resolution of 0.3 arcsec is assumed. In the case of VIMOS,<br />
this is simply the number of spaxels.<br />
• 3D power is the product of spatial and spectral power<br />
One interesting number is the Etendue, which is directly linked to the speed <strong>for</strong> per<strong>for</strong>ming a<br />
survey. Because of its large field of view and better throughput, MUSE is more than ten times<br />
faster than VIMOS. Another key number is the 3D power, a number that measures the<br />
datacube in<strong>for</strong>mation content that could be explored by the instrument. In this respect, MUSE<br />
is more than 2 orders of magnitude better than VIMOS.<br />
These figures of merit are just an indicator to facilitate a quantifiable comparison. The<br />
capability of an instrument to conduct very faint-object science depends on a number of
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parameters, which are generally not easy to quantify, such as the accuracy of sky subtraction,<br />
PSF stability, minimization of diffuse light, etc. However, optimizing such key aspects of the<br />
instrument per<strong>for</strong>mance <strong>for</strong>ms the very basis upon which MUSE has been designed and shall<br />
be built, and we are confident that this will ultimately ensure the achievement of our aims.<br />
8.3. High spatial resolution IFU<br />
In contrast to wide-field IFUs, which are not numerous, t<strong>here</strong> is a growing number of AOassisted<br />
IFUs in development or in operation. In the following table we show the main<br />
competitors (operating or planned) <strong>for</strong> 8m telescopes.<br />
Instrument GNIRS+IFU NIFS OSIRIS SINFONI MUSE<br />
Telescope Gemini S Gemini N Keck VLT VLT<br />
Multiplex type Slicer IFU Slicer IFU Lenslet IFU Slicer IFU Slicer IFU<br />
No. spatial elements 620 2000 1000 1000 90,000<br />
Spatial sampling,<br />
arcsec/pixel<br />
0.07x0.07 0.04x0.10 0.02<br />
0.05<br />
0.10<br />
FOV (arcsec) 2.2x1.5 3.0x2.9 1.28x0.32<br />
3.20x0.80<br />
6.40x1.60<br />
0.025<br />
0.10<br />
0.25<br />
0.8x0.8<br />
3.2x3.2<br />
8x8<br />
0.025<br />
7.5x7.5<br />
Spectral elements 1000 2000 1300 2000 4000<br />
Spectral resolutions 1800, 6000 5300 3800 4000 3000<br />
Wavelength range 0.9-2.5 µm 0.9-2.5 µm 1-2.5 µm 1-2.5 µm 0.46-0.93 µm<br />
Detector 1kx1k InSb 2k x 2k<br />
HgCdTe<br />
2k x 2k 2k x 2k 24x4kx4k<br />
CCD<br />
Date comm. 2003 (NS) 2005 2004 2004 2011<br />
Table 8-2: Existing or planned AO assisted IFU on 8m class telescopes<br />
In the following we have focused our comparison with SINFONI which is available at VLT,<br />
but most of what will follow is also be valid <strong>for</strong> the other instruments. We limit our<br />
comparison to the 25 milli-arcsec sampling of SINFONI.<br />
One can then per<strong>for</strong>m the same computation as in previous subsection. This gives a gain of 90<br />
in Etendue 10 and 135 in 3D power <strong>for</strong> MUSE with respect to SINFONI. But the key<br />
parameter is the spatial resolution given by the AO system. It is well known that AO<br />
per<strong>for</strong>mance is much better in the infrared than in the optical. The SINFONI predicted<br />
per<strong>for</strong>mances are quite good, with 50% Strehl ratio in the K band. However, this per<strong>for</strong>mance<br />
is obtained only with a bright, natural on-axis guide star (V
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However it shows that MUSE NFM should achieve similar or better spatial per<strong>for</strong>mance than<br />
SINFONI, with the advantage of a much larger field of view.<br />
Another parameter is the sensitivity. For example, the published SINFONI surface brightness<br />
sensitivity gives K=12.7 magnitude.arcsec -2 , <strong>for</strong> a one hour exposure, w<strong>here</strong>as MUSE ETC<br />
gives I AB =17 arcsec -2 in the same conditions. It must also be emphasized that, with their<br />
comparable spatial resolutions and distinct wavelength coverage, MUSE NFM and SINFONI<br />
are remarkably complementary.<br />
Finally, with similar or better spatial resolution, much larger field of view and better<br />
sensitivity, MUSE should have the per<strong>for</strong>mance gain that one would expect <strong>for</strong> an instrument<br />
coming into operation at VLT seven years later.
Exposure Time<br />
Calculator and<br />
Per<strong>for</strong>mance Analysis<br />
Written by : R. Bacon<br />
<strong>Institute</strong> : CRAL<br />
Reference : MUSE-MEM-SCI-051<br />
Issue : 1.3<br />
Date : 28/01/04<br />
File :<br />
muse_etc.doc<br />
Distribution : ESO<br />
History:<br />
• 1.0 – 22/12/03 – Initial version with inputs from Simon Morris and Ian Parry<br />
• 1.1 – 09/01/04 – Comments by Richard Mc Dermid<br />
• 1.2 – 15/01/04 – Comments by Luca Pasquini<br />
• 1.3- 28/01/04 – Final Phase A release
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
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1. Introduction ........................................................................................................................ 3<br />
2. Documents.......................................................................................................................... 3<br />
2.1. Applicable documents ................................................................................................ 3<br />
2.2. Reference documents ................................................................................................. 3<br />
3. Acronyms ........................................................................................................................... 3<br />
4. Assumptions....................................................................................................................... 5<br />
5. Results ................................................................................................................................ 6<br />
5.1. Wide-field mode......................................................................................................... 6<br />
Extended source .................................................................................................................6<br />
Unresolved source.............................................................................................................. 7<br />
5.2. Narrow field mode ..................................................................................................... 8<br />
Extended source .................................................................................................................8<br />
Unresolved source.............................................................................................................. 8<br />
6. Analysis.............................................................................................................................. 9<br />
6.1. Wavelength dependency ............................................................................................ 9<br />
6.2. Improvement due to AO............................................................................................. 9<br />
6.3. Noise regime ............................................................................................................ 10<br />
Wide field mode............................................................................................................... 10<br />
Narrow field mode ........................................................................................................... 10<br />
6.4. Centering star ........................................................................................................... 10<br />
6.5. Other models of throughput ..................................................................................... 10<br />
7. Limitations ....................................................................................................................... 12<br />
8. Plan <strong>for</strong> phases B & C...................................................................................................... 12<br />
ANNEX – ETC mathcad sheet................................................................................................. 13
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
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1. Introduction<br />
This document describes the MUSE exposure time calculator developed during phase A and<br />
discusses the instrument per<strong>for</strong>mances. Limiting flux and magnitude quoted in the Science<br />
Case document refer to these ETC results.<br />
2. Documents<br />
2.1. Applicable documents<br />
AD1 MUSE Top Instrumental Parameters<br />
AD2 MUSE AO analysis report<br />
AD3 MUSE System analysis and budgets<br />
AD4 MUSE Instrument detector system specification<br />
MUSE-MEM-SCI-016<br />
VLT-TRE-ESO-14675-2951<br />
MUSE-MEM-TEC-031<br />
MUSE-MEM-TEC-024<br />
2.2. Reference documents<br />
RD1 ESO ETC web pages<br />
RD2 A flux calibrated, high resolution atlas of optical<br />
emission sky from UVES<br />
RD4 MUSE Science Case<br />
Hanuschik R.W, 2003, A&A, 407,<br />
1157<br />
MUSE-MEM-SCI-052<br />
3. Acronyms<br />
AD<br />
AO<br />
CCD<br />
ESO<br />
ETC<br />
FoV<br />
FWHM<br />
INM<br />
MUSE<br />
NA<br />
NFM<br />
PSF<br />
R<br />
RD<br />
Applicable Document<br />
Adaptive Optics<br />
Charge-Coupled Device<br />
European Southern Observatory<br />
Exposure Time Calculator<br />
Field of View<br />
Full Width Half Maximum<br />
Instrument Numerical Model<br />
Multi Unit Spectroscopic Explorer<br />
Not Applicable<br />
Narrow Field Mode<br />
Point Spread Function<br />
Spectral Resolving Power<br />
Reference Document
S/N<br />
TBC<br />
TBD<br />
VLT<br />
WFM<br />
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
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Signal over noise<br />
To Be Confirmed<br />
To Be Defined<br />
Very Large Telescope<br />
Wide Field Mode
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
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4. Assumptions<br />
Mathematics and detail computation can be found in the appendix. All important assumptions<br />
and input parameters are shown in following table.<br />
Item Assumptions Remark<br />
Sky brightness Continuum only (outside OH emission lines),<br />
reference RD2, moon aged of 5 days<br />
S/N estimate is only valid<br />
outside OH lines (see RD1<br />
<strong>for</strong> an estimate of the free<br />
OH fraction of spectral<br />
range)<br />
Atmospheric Paranal extinction (reference RD1)<br />
An airmass of 1 is assumed<br />
extinction<br />
Telescope 485425.1 cm² (reference RD1)<br />
effective area<br />
Instrument<br />
throughput in WF<br />
Reference AD3<br />
Typical curve with adaptive<br />
secondary<br />
mode<br />
Instrument Provisionally taken equal to WF mode Overestimated by 5%<br />
throughput in HR<br />
mode<br />
CCD dark current 3 electrons/hour (reference AD4) Typical value<br />
CCD readout 4 electrons (reference AD4) Fairchild 4k x 4k<br />
Spatial PSF 4 cases considered: poor (1.1 arcsec, 70%-tile) Current Paranal statistics<br />
and good (0.65 arcsec, 30%-tile) seeing (5/99-8/02)<br />
conditions, with and without AO. Simulations<br />
take into account PSF variation with wavelength<br />
(VLT-TRE-ESO-14675-2951). All PSFs are<br />
convolved with MUSE image quality, assumed to<br />
be 0.254 arcsec FWHM (AD1)<br />
Number<br />
summed<br />
pixels (1)<br />
of<br />
spatial<br />
3x3 pixels (0.6x0.6 arcsec²) in good seeing<br />
conditions and 4x4 pixels (0.8x0.8 arcsec²) in<br />
poor seeing conditions, both <strong>for</strong> AO and non AO<br />
observations<br />
For spatially unresolved<br />
source. Object flux fraction<br />
recovered is 40-60%.<br />
Spectral PSF Gaussian shape of 2 pixels FWHM<br />
Number of 3 pixels <strong>for</strong> emission line source, 1 or 10 pixels 92% fraction of flux<br />
summed spectral <strong>for</strong> respectively full and low spectral resolution enclosed in case of<br />
pixels (2) continuum<br />
emission line source<br />
Exposure time 1 hour Limited by cosmic ray<br />
impacts<br />
Number of 80 <strong>for</strong> deep field and 1 <strong>for</strong> shallow field<br />
exposure<br />
Limiting S/N 5 <strong>for</strong> 1 resolution element A resolution element being<br />
defined in (1) and (2)
5. Results<br />
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
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5.1. Wide-field mode<br />
Extended source<br />
The following two tables give the instrument per<strong>for</strong>mance at full spectral resolution in case of<br />
a spatially extended source with a flat continuum spectral distribution (AB surface magnitude)<br />
or an unresolved emission line (line flux by arcsec² in 10 -19 erg.s -1 .cm -2 units). Two cases are<br />
considered, a single exposure of 1 hour (shallow field) and a series of 80 exposures of 1 hour<br />
(deep field). Values are given at central wavelength of photometric band, except <strong>for</strong> B’ and z’<br />
which are set to the limits of the MUSE spectral range.<br />
Shallow Field Observations (1h) – Extended source<br />
λ (µm) Band AB arcsec -2 Line flux arcsec -2<br />
0.465 B’ 20.5 595.6<br />
0.55 V 21.2 221.3<br />
0.64 R 21.3 154.1<br />
0.79 I 20.8 153.4<br />
0.93 z’ 20.0 221.9<br />
Deep Field Observations (80x1h) – Extended source<br />
λ (µm) Band AB arcsec -2 Line flux arcsec -2<br />
0.465 B’ 23.28 53.8<br />
0.55 V 23.87 21.4<br />
0.64 R 23.93 15.0<br />
0.79 I 23.48 14.9<br />
0.93 z’ 22.78 20.4
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
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Unresolved source<br />
The next two tables display the limiting magnitude and line emission flux (in 10 -19 erg.s -1 .cm -2<br />
units) in the case of spatially unresolved object. Various conditions have been explored <strong>for</strong><br />
the spatial PSF: seeing limited observations (non AO column) and AO observation, each in<br />
two atmospheric conditions: good (seeing of 0.65 arcsec) and poor (seeing of 1.1 arcsec). To<br />
retrieve a significant fraction of the object flux, we have summed in an area of 0.6x0.6 arcsec²<br />
in the case of good seeing conditions and 0.8x0.8 arcsec² in the case of poor seeing. A low<br />
spectral resolution limiting magnitude at a tenth of the nominal spectral resolution is also<br />
given (obtained by summation of ten spectral pixels and assuming a flat continuum spectral<br />
distribution). Shallow (1h) and deep (80x1h) exposures are presented.<br />
Shallow Field Observations (1h) – Unresolved Source<br />
λ (µm) Band AB full R AB R/10 Line Flux<br />
Atm. cond Poor Good Poor Good Poor Good<br />
0.465 B’<br />
Non AO 21.7 22.1 23.0 23.5 223.3 144.4<br />
AO 21.8 22.4 23.1 23.7 199.0 111.2<br />
0.55 V<br />
Non AO 22.4 22.8 23.7 24.2 84.2 53.5<br />
AO 22.7 23.1 24.0 24.5 64.1 40.9<br />
0.64 R<br />
Non AO 22.5 22.9 23.8 24.3 56.4 36.3<br />
AO 22.8 23.2 24.1 24.6 42.5 27.4<br />
0.79 I<br />
Non AO 22.1 22.6 23.4 23.9 52.2 33.4<br />
AO 22.4 22.9 23.7 24.2 38.7 25.3<br />
0.93 z’<br />
Non AO 21.4 21.9 22.8 23.2 68.7 44.8<br />
AO 21.8 22.2 23.1 23.5 49.7 33.7<br />
Deep Field Observations (80x1h) – Unresolved Source<br />
λ (µm) Band AB full R AB R/10 Line Flux<br />
Atm. cond Poor Good Poor Good Poor Good<br />
0.465 B’<br />
Non AO 24.1 24.6 25.4 25.9 23.6 15.0<br />
AO 24.3 24.9 25.5 26.2 21.1 11.6<br />
0.55 V<br />
Non AO 24.8 25.3 26.1 26.6 9.1 5.7<br />
AO 25.1 25.6 26.4 26.9 6.9 4.4<br />
0.64 R<br />
Non AO 24.9 25.4 26.2 26.7 6.1 3.9<br />
AO 25.2 25.7 26.5 27.0 4.6 2.9<br />
0.79 I<br />
Non AO 24.5 25.0 25.8 26.3 5.6 3.6<br />
AO 24.9 25.3 26.1 26.6 4.2 2.7<br />
0.93 z’<br />
Non AO 23.9 24.4 25.2 25.6 7.3 4.7<br />
AO 24.3 24.7 25.5 26.0 5.3 3.5
5.2. Narrow field mode<br />
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 8/14<br />
Extended source<br />
The following table gives the instrument per<strong>for</strong>mance at full spectral resolution in case of a<br />
spatially extended source with a flat continuum spectral distribution (AB surface magnitude)<br />
or an unresolved emission line (line flux by arcsec² in 10 -19 erg.s -1 .cm -2 units). Values are<br />
given at central wavelength of photometric band, except <strong>for</strong> B’ and z’ which are set to the<br />
limits of the MUSE spectral range.<br />
Typical Observations (1h) – Extended source<br />
λ (µm) Band AB arcsec -2 Line flux arcsec -2<br />
0.465 B’ 16.49 2564.0<br />
0.55 V 17.21 702.6<br />
0.64 R 17.35 472.6<br />
0.79 I 16.95 480.2<br />
0.93 z’ 15.93 899.3<br />
Unresolved source<br />
The next tables display the limiting magnitude and line emission flux (in 10 -19 erg.s -1 .cm -2<br />
units) in the case of spatially unresolved object. Only AO observation in good seeing (0.65<br />
arcsec) conditions is considered. To retrieve a significant fraction of the object flux, we have<br />
summed in an area of 0.075x0.075 arcsec. A low spectral resolution limiting magnitude at a<br />
tenth of the nominal spectral resolution is also given (obtained by summation of ten spectral<br />
pixels and assuming a flat continuum spectral distribution).<br />
Typical Observations (1h) – Unresolved source<br />
λ (µm) Band AB full R AB R/10 Line flux<br />
0.465 B’ 21.08 23.06 214.8<br />
0.55 V 22.00 24.49 42.6<br />
0.64 R 22.30 24.85 22.8<br />
0.79 I 22.09 24.61 18.6<br />
0.93 z’ 21.66 23.75 28.6
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
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6. Analysis<br />
6.1. Wavelength dependency<br />
The computed limiting flux is more or less<br />
constant with wavelength, except in the<br />
blue w<strong>here</strong> it shows a rapid decrease short<br />
ward 0.55 µm. This is partly due to the<br />
lower throughput in the blue (as shown in<br />
figure 1) plus a small contribution by<br />
extinction. In the red, the lower throughput<br />
is balanced by the linear increase of the<br />
number of photon per second with<br />
wavelength <strong>for</strong> a given flux.<br />
6.2. Improvement due to AO<br />
The previously listed per<strong>for</strong>mances show<br />
little difference between AO and non AO<br />
detection: the gain is 0.2-0.3 magnitude in<br />
continuum and 30% in line flux. This is<br />
Figure 1: Variation of throughput (dashed line) and limiting<br />
flux (solid line) with wavelength.<br />
due to the relatively large area (9 or 16 pixels) used to recover the object flux. On the other<br />
hand, if we restrict to the central pixel, we have a much larger difference. An example in<br />
shown in the following table, with 0.8 magnitude gain and 100% gain in flux between AO and<br />
non AO observations.<br />
Deep Field Observations (80x1h) – Unresolved Source – Central pixel only<br />
λ (µm) Band AB full R AB R/10 Line Flux<br />
Atm. cond Poor Good Poor Good Poor Good<br />
Non AO 23.5 24.3 24.8 25.6 14.0 6.7<br />
0.79 I<br />
AO 24.2 25.1 25.5 26.4 7.5 3.4
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 10/14<br />
6.3. Noise regime<br />
Wide field mode<br />
The following table presents the worst case of noise variance distribution computed in the<br />
case of deep field observation of an unresolved source and in poor seeing conditions (non AO<br />
mode).<br />
Typical noise variance distribution in wide field mode<br />
λ (µm) Band Object Sky Read Noise Dark Current<br />
0.465 B’ 1.3% 45.7% 44.6% 8.4%<br />
0.55 V 0.9% 75.2% 20.1% 3.8%<br />
0.64 R 0.9% 77.2% 18.4% 3.5%<br />
0.79 I 0.9% 76.0% 19.4% 3.6%<br />
0.93 z’ 1.2% 53.7% 37.9% 7.1%<br />
It shows that we are in photon noise regime in most of the wavelength range with less than<br />
25% of the total variance due to detector noise. It is only at the two extreme wavelengths that<br />
the detector noise fraction reaches half of the total variance. These results are <strong>for</strong> a<br />
conservative value of 4 electron readout detector noise. Dark current is almost negligible.<br />
Narrow field mode<br />
Typical noise variance distribution in narrow field mode<br />
λ (µm) Band Object Sky Read Noise Dark Current<br />
0.465 B’ 19.4% 3.5% 65.0% 12.2%<br />
0.55 V 18.5% 11.5% 59.0% 11.1%<br />
0.64 R 18.3% 12.7% 58.1% 10.9%<br />
0.79 I 18.4% 12.0% 58.6% 11.0%<br />
0.93 z’ 19.2% 4.7% 64.0% 12.0%<br />
As expected in the narrow field mode, the sky contribution is becoming much smaller in the<br />
25 milliarcsec pixel and we are then in a detector noise regime. An improvement of detector<br />
read-out noise will have a major impact in this mode.<br />
6.4. Centering star<br />
Optimal merging of the 80 individual 1 hour exposure into the final deep field datacube will<br />
required a star bright enough to allow accurate centering. According to the ETC a star brighter<br />
than 22.8 R AB magnitude will reach a S/N of 50 after rebinning at low spectral resolution<br />
(R~30) resolution. Even at this low spectral resolution, the full spectral range is sample with<br />
20 points and will allow a good estimate of the spatial PSF and its variation with wavelength.<br />
6.5. Other models of throughput<br />
In the different throughput models presented in AD1, we have selected the typical curve<br />
model. Although we think that this model is a realistic goal, it might be considered as difficult
to achieve. To show the importance of<br />
throughput, we present in the figure 2<br />
a per<strong>for</strong>mance comparison when using<br />
the worst and best case models.<br />
As it can be seen, t<strong>here</strong> is a significant<br />
difference between the worst and<br />
typical curve. The limiting flux is<br />
increased by 30% from 3 to 4<br />
10 -19 erg.s -1 .cm -2 . Although this is not<br />
negligible, this is still in phase with the<br />
deep field science case. Limiting<br />
magnitude difference between the best<br />
and typical throughput curves is<br />
especially important in the red, with a<br />
decrease by a factor 2 at 0.93 µm.<br />
Having such a throughput (mainly due<br />
to CCD QE), will be very benefit <strong>for</strong><br />
the deep field science case and it<br />
should be a goal <strong>for</strong> phase B study.<br />
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 11/14<br />
Figure 2: Limiting deep-field flux (bottom figure) in<br />
10 -19 erg.s -1 .cm -2 <strong>for</strong> 3 different throughput models:<br />
typical (solid line), worst case (dashed line) and best<br />
case (point-dashed line). The corresponding<br />
throughput curves are shown in the top figure.
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 12/14<br />
7. Limitations<br />
The ETC does not take into account any possible systematic such as flat field residuals and its<br />
results should t<strong>here</strong><strong>for</strong>e be considered as optimistic. These 2 nd order effects are by definition<br />
difficult to model in this simple method. We plan to have a more realistic approach using the<br />
Instrument Numerical Model (INM). Results from the end-to-end model will be compared to<br />
the ETC results.<br />
One possible concern is the accuracy of sky subtraction which may be difficult to achieve in<br />
the absence of a beam switching or nod and shuffle technics 1 . Outside OH lines, the sky<br />
brightness is around 410 -19 erg.s -1 .cm -2 .Å -1 .pixel -1 and is nearly constant in our spectral range.<br />
This is 40 times larger than the faintest object we can detect which translate into a few percent<br />
precision of sky subtraction. Our experience with SAURON deep fields (see Science Case in<br />
RD4) shows that it is easy to correct a factor 10. The remaining factor 4 improvement should<br />
be achievable since, unlike SAURON, MUSE will be specifically designed <strong>for</strong> deep field<br />
projects and optimized <strong>for</strong> very long integration. However this is seen as a critical point and<br />
will be addressed in depth in the next project phases.<br />
The ETC point-like sensitivity is based on a summation over a spatial area corresponding to<br />
roughly half the object flux. This is a simplistic method and could be improved using optimal<br />
summation scheme taking into account the real spatial distribution of signal and noise. We<br />
plan to estimate the corresponding gain using the INM and simulated deep fields.<br />
8. Plan <strong>for</strong> phases B & C<br />
In the next phases of the project we will maintain the ETC up to date with the instrument<br />
per<strong>for</strong>mances. The detailed design should allow a better estimate of throughput, image quality<br />
and detector characteristics, and further AO simulations should improve our knowledge of the<br />
expected spatial PSF. At the end of phase B, the IFU prototype will also give empirical data<br />
with which to calibrate the ETC.<br />
The ETC will be made available to the science team, either via a web interface or via portable<br />
software. To ensure accurate and realistic results, we will extensively compare ETC results<br />
with full end-to-end simulations using simulated object datacubes, the instrument numerical<br />
model and data reduction and analysis software. Updated ETC results will be reassas and<br />
optimize the observation strategy accordingly.<br />
1 These technics are not applicable to the deep field given that object and sky locations are unknown and<br />
wavelength dependant.
ANNEX – ETC mathcad sheet<br />
Roland Bacon<br />
version 1.0 11-05-03<br />
Inspired from Simon Morris mathcad and Ian Parry excel ETC<br />
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 13/14<br />
version 2.0 8-06-03 Take sky value (no OH) from Hanushik paper<br />
add variation of ensquared energy with wavelength, use updated version 1.1 of<br />
throughput<br />
version 3.0 02-10-03<br />
Refurbish and simplify the presentation<br />
updated version 2.1 of throughput<br />
include also bad seeing conditions <strong>for</strong> AO per<strong>for</strong>mances and add effect of MUSE IQE<br />
on all PSFs<br />
version 3.1 09-10-03<br />
Change z = 0.95 µm and B=0.44 µm traditional wavelength to the red and blue limits<br />
of MUSE (respectively 0.93 µm and 0.465 µm)<br />
version 3.2 11-11-03<br />
Add computation of accuracy needed in sky subtraction<br />
version 3.3 1-12-03<br />
Updated version 20/11/03 of throughput with VLT adaptative secondary AO system,<br />
typical curve. Added computation of surface line emission sensitivity.
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 14/14<br />
1. Units and Constant<br />
_______________________________________________________________________________<br />
Velocity of light in vacuum c<br />
:= 299792458m ⋅ ⋅s − 1<br />
Angstroem A := 10 − 10 ⋅m<br />
microns µm:=<br />
10 − 6<br />
⋅m<br />
Planck's constant (h) h 6.626075510 − 34<br />
:=<br />
⋅<br />
⋅ joule⋅sec<br />
phot := 1<br />
deg<br />
deg<br />
arcsec := arcmin :=<br />
3600<br />
60<br />
elec := 1<br />
hour := 3600⋅<br />
s<br />
_______________________________________________________________________________<br />
back<br />
2. Define a few useful functions<br />
b<br />
⌠<br />
⎮ fx ( ) dx<br />
⌡<br />
a<br />
Mean( f, a,<br />
b)<br />
:=<br />
b − a<br />
⎛<br />
⎞<br />
exp⎜<br />
−r 2<br />
a<br />
⎜<br />
2 σ 2<br />
⌠<br />
⎝ ⋅ ⎠<br />
⎮ 2<br />
GAUSS( r,<br />
σ)<br />
:= E GAUSS ( a,<br />
σ)<br />
:= ⎮<br />
2⋅π<br />
⋅σ<br />
⎮<br />
⌡−<br />
a<br />
2<br />
FWHM GAUSS ( σ) := 2 2⋅ln( 2)<br />
⋅σ<br />
GAUSS( x,<br />
σ)<br />
dx<br />
σ GAUSS ( FWHM)<br />
:=<br />
FWHM<br />
( )<br />
2 2⋅ln( 2)<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 15/14<br />
3. Photometric System<br />
3.1 UBVRIz System<br />
⎛<br />
Bessel, 1979, PASP 91, 589<br />
⎞<br />
⎛ ⎞<br />
⎜<br />
⎟<br />
⎜<br />
7.1804<br />
⎟<br />
⎟<br />
⎜ 7.4425 ⎟<br />
⎟<br />
⎜ ⎟<br />
7.6408<br />
⎟<br />
⎜ ⎟<br />
⎟<br />
⎜ 7.9115<br />
⎟⋅µm<br />
8.1101<br />
⎟<br />
⎜<br />
⎟<br />
:=<br />
⎟<br />
⎜ ⎟<br />
⎟<br />
⎜ 8.4989 ⎟<br />
⎟<br />
⎜ 8.9706 ⎟<br />
⎟<br />
⎜ ⎟<br />
⎟<br />
⎜ 9.4367 ⎟<br />
⎟<br />
⎜ 10.2649⎟<br />
⎜<br />
⎠<br />
⎝ 10.2692⎠<br />
0.36<br />
7.3788<br />
⎜<br />
⎜<br />
0.44<br />
⎜ 0.55<br />
⎜<br />
0.64<br />
⎜<br />
⎜ 0.79<br />
λ b := ⎜ 0.95 val_Z<br />
⎜<br />
b<br />
⎜ 1.25<br />
⎜ 1.65<br />
2.2<br />
3.5<br />
4.8<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
Magnitude central wavelengths and zero<br />
points from ESO web site<br />
http://www.eso.org/observing/etc/doc/ge<br />
n/<strong>for</strong>mulaBook/node12.html<br />
Central wavelengths to be used<br />
Useful reference wavelength <strong>for</strong> MUSE<br />
λ B := 0.465 ⋅µm<br />
λ V := λ b2 λ R := λ b3 λ I := λ b4 λ z := 0.93 ⋅µm<br />
⎛<br />
λ B<br />
⎜<br />
⎛ "B"<br />
⎜ λ V ⎟<br />
⎜<br />
"V"<br />
⎜ ⎟<br />
⎜<br />
λ λ MUSE := ⎜ R ⎟<br />
Band MUSE := ⎜ "R"<br />
⎟<br />
⎜<br />
λ "I"<br />
I ⎟<br />
⎜<br />
⎝ "z"<br />
λ z<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
⎠<br />
( )<br />
( , , val_Z b , λ )<br />
spline_Z b := lspline λ b , val_Z b<br />
λ := 0.36 ⋅µm, 0.36 ⋅µm<br />
+ 0.01 ⋅µm..<br />
1.25 ⋅µm<br />
Z b ( λ) := interp spline_Z b λ b<br />
i := 0..<br />
6<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
Note that B and z wavelength are set to the limit<br />
of MUSE wavelength range<br />
8.5<br />
Z b<br />
( λ)<br />
8<br />
val_Z bi<br />
7.5<br />
7<br />
0.5 1<br />
λ<br />
λ bi<br />
,<br />
µm µm
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 16/14<br />
Function to trans<strong>for</strong>m magnitude in flux<br />
Mag2Flux( mag,<br />
λ) 10 − 0.4⋅mag<br />
Z b<br />
:=<br />
− ( λ)<br />
⋅W⋅ m − 2 ⋅µm − 1<br />
SurfMag2Flux( mag,<br />
λ) 10 − 0.4⋅mag<br />
Z b<br />
:=<br />
− ( λ)<br />
⋅W⋅ m − 2 ⋅µm − 1 ⋅arcsec − 2<br />
Flux2Mag( F,<br />
λ) := −2.5⋅<br />
⎡<br />
⎢<br />
⎣<br />
log<br />
⎡<br />
⎢<br />
⎣<br />
F<br />
Wm ⋅ − 2 ⋅µm − 1<br />
( )<br />
⎤<br />
⎥<br />
⎦<br />
⎤<br />
⎥⎦<br />
+ Z b ( λ)<br />
Flux2MagSurf( F,<br />
λ) := Flux2Mag( F,<br />
λ) − 2.5⋅<br />
log⎡ ( arcsec<br />
2 )<br />
⎣<br />
⎤<br />
⎦<br />
back<br />
3.2 AB magnitude system<br />
Flux2AB F λ , λ<br />
( ) := −2.5<br />
⎡<br />
F λ ⋅λ 2<br />
⋅ ⎢<br />
⎥<br />
log<br />
⎢<br />
c erg⋅cm − 2 ⋅sec − 1 ⋅Hz − 1 −<br />
⎥<br />
48.60<br />
⎣<br />
⋅( )<br />
⎤<br />
⎦<br />
AB2Flux( AB,<br />
λ)<br />
−<br />
10 0.4⋅(<br />
AB + 48.60 )<br />
:=<br />
λ 2 ⋅c⋅erg⋅cm − 2 ⋅s − 1 ⋅Hz − 1<br />
Flux2ABSurf F λ , λ<br />
( ) := −2.5<br />
⎡<br />
F λ ⋅λ 2<br />
⋅ ⎢<br />
⎥<br />
log<br />
⎢<br />
c erg⋅cm − 2 ⋅sec − 1 ⋅Hz − 1 ⋅arcsec − 2 −<br />
⎥<br />
48.60<br />
⎣<br />
⋅( )<br />
⎤<br />
⎦<br />
SurfAB2Flux( AB,<br />
λ)<br />
−<br />
10 0.4⋅(<br />
AB + 48.60 )<br />
:=<br />
λ 2 ⋅c⋅erg⋅cm − 2 ⋅s − 1 ⋅Hz − 1 ⋅arcsec − 2<br />
Test<br />
( ( ),<br />
λ R ) = 25.163<br />
Flux2AB Mag2Flux 25,<br />
λ R<br />
SurfAB2Flux 25,<br />
λ R<br />
( ) = 2.657 10 − 19<br />
× erg⋅cm − 2 ⋅s − 1 ⋅A − 1 ⋅arcsec − 2<br />
( ) = 2.657 10 − 19<br />
AB2Flux 25,<br />
λ R<br />
× erg⋅cm − 2 ⋅s − 1 ⋅A − 1<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 17/14<br />
4. Sky brightness<br />
Sky brightness is taken from the Hanuschik paper, it doesnt include the OH lines<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
0.44<br />
0.1<br />
0.5 ⎟<br />
⎜ 0.1<br />
0.55 ⎟<br />
⎜ 0.105<br />
⎟<br />
⎜<br />
0.6<br />
0.095<br />
⎟<br />
⎜<br />
0.65 ⎟<br />
⎜ 0.08<br />
⎟<br />
⎜<br />
0.7<br />
0.075<br />
⎜ ⎟<br />
⎜<br />
λ Sky := ⎜ 0.75 ⎟⋅µm<br />
TabFlux SkyNoOH := ⎜ 0.075<br />
⎜ 0.8 ⎟<br />
⎜ 0.082<br />
⎜ ⎟<br />
⎜ 0.85 ⎟<br />
0.07<br />
⎜ 0.9 ⎟<br />
0.06<br />
⎜ ⎟<br />
⎜<br />
0.95<br />
⎟<br />
0.06<br />
⎜ 1.0 ⎟<br />
0.1<br />
⎜<br />
1.025<br />
0.15<br />
⎝<br />
⎞<br />
⎠<br />
Spline_Flux SkyNoOH<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
:= lspline( λ Sky , TabFlux SkyNoOH )<br />
Flux SkyNoOH ( λ) := interp Spline_Flux SkyNoOH , λ Sky , TabFlux SkyNoOH , λ<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟⋅<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
( )<br />
⎠<br />
10 − 16 ⋅erg⋅s − 1 ⋅cm − 2 ⋅A − 1 ⋅arcsec − 2<br />
λ := 0.44 ⋅µm, 0.47 ⋅µm..<br />
1.025 ⋅µm<br />
Sky Flux in erg/cm²/s/A/arcsec²<br />
1 .10 17<br />
2 . 10 17 Wavelength (µm)<br />
0<br />
0.4 0.5 0.6 0.7 0.8 0.9 1 1.1
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 18/14<br />
Checking<br />
( ( ) λ B ) 21.766<br />
( ( ),<br />
λ V ) 21.337<br />
( ( ),<br />
λ R ) 21.109<br />
( ( ),<br />
λ I ) 20.441<br />
( ( ),<br />
λ z ) 20.378<br />
Flux2ABSurf Flux SkyNoOH λ B ,<br />
Flux2ABSurf Flux SkyNoOH λ V<br />
Flux2MagSurf Flux SkyNoOH λ R<br />
Flux2MagSurf Flux SkyNoOH λ I<br />
Flux2MagSurf Flux SkyNoOH λ z<br />
= ESO ETC value 22.7<br />
= ESO ETC value 21.8<br />
= ESO ETC value 20.9<br />
= ESO ETC value 19.9<br />
= ESO ETC value 18.8<br />
Note the difference in the red is fully explained by the OH suppression. The difference in the<br />
blue is probably due to the moon light, a moon aged of 5 days would make the difference.<br />
19<br />
Sky brightness (excluding OH lines)<br />
AB magnitude/arcsec²<br />
20<br />
21<br />
22<br />
0.4 0.6 0.8 1<br />
Wavelength (µm)<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 19/14<br />
tab_extinct:=<br />
0<br />
1<br />
2<br />
3<br />
4<br />
5<br />
6<br />
7<br />
8<br />
9<br />
0 1<br />
440 0.26<br />
450 0.25<br />
460 0.22<br />
470 0.21<br />
480 0.21<br />
490 0.18<br />
500 0.17<br />
520 0.16<br />
540 0.14<br />
560 0.13<br />
5. Atmospheric extinction<br />
Reference: Paranal extinction - ESO<br />
VIMOS ETC<br />
( ) 0<br />
λext 10 − 3<br />
〈〉<br />
⋅ µm<br />
〈<br />
:= ⋅ tab_extinct val_extinct tab_extinct 1 〉<br />
:=<br />
⎛<br />
⎝<br />
pol_extinct:=<br />
régress⎜<br />
λext<br />
µm , val_extinct,<br />
4<br />
⎛<br />
⎝<br />
λext<br />
λ<br />
int_extinct ( λ) := interp⎜<br />
pol_extinct, , val_extinct,<br />
µm<br />
µm<br />
⎞<br />
⎠<br />
⎞<br />
⎠<br />
Extinct( λ , Airmass) := 10 − 0.4⋅int_extinctλ<br />
( ) ⋅Airmass<br />
λ := 0.45 ⋅µm, 0.46 ⋅µm..<br />
1 ⋅µm<br />
0.4<br />
int_extinctλ ( )<br />
val_extinct<br />
0.2<br />
0<br />
0.5 0.6 0.7 0.8 0.9<br />
λ ⋅µm − 1 , λext ⋅µm − 1<br />
1<br />
Extinction Factor<br />
Extinct( λ,<br />
1.0)<br />
0.9<br />
0.8<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ ⋅µm − 1<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 20/14<br />
6. Telescope Effective Area<br />
Area VLT := 485425.1cm ⋅<br />
2 From ESO UVES ETC<br />
Note: Useful surface is only<br />
Area VLT<br />
π ⋅( 4⋅m) 2<br />
= 0.966<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 21/14<br />
7. MUSE throughput<br />
7.1 MUSE throughput of WF mode<br />
table_muse_throughput:=<br />
0<br />
1<br />
2<br />
3<br />
0 1<br />
0.46 0.0784<br />
0.48 0.1217<br />
0.5 0.1681<br />
0.52 0.2092<br />
Total throughput of MUSE,<br />
excluding atmosp<strong>here</strong>, version<br />
20/11/03<br />
Typical curve with Adaptive<br />
Secondary<br />
4<br />
0.54 0.2452<br />
5<br />
0.56 0.273<br />
6<br />
0.58 0.2923<br />
7<br />
0.585 0.2973<br />
8<br />
0.59 0.3012<br />
9<br />
0.595 0.3046<br />
〈〉<br />
λ_table := µm⋅<br />
table_muse_throughput 0<br />
〈<br />
val_muse_throughput table_muse_throughput 1 〉<br />
:=<br />
T MUSE ( λ) := interplin( λ_table, val_muse_throughput,<br />
λ)<br />
( ) = 0.239<br />
λ min := 0.465 ⋅µm<br />
λ max := 0.93 ⋅µm<br />
Mean T MUSE , λ min , λ max<br />
λ := λ min , λ min + 0.001 ⋅µm..<br />
λ max<br />
0.4<br />
MUSE+VLT Total Throughput<br />
0.35<br />
0.3<br />
0.25<br />
T MUSE<br />
( λ)<br />
0.2<br />
0.15<br />
0.1<br />
0.05<br />
0<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 22/14<br />
7.2 MUSE throughput of HR mode
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 23/14<br />
DN CCD<br />
RN CCD<br />
:= Dark Current<br />
3⋅<br />
elec<br />
hour<br />
8. MUSE CCD characteristics<br />
:= 4⋅elec<br />
Readout noise Note; This is <strong>for</strong> Fairchild CCD<br />
Npix CCD := 4096<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 24/14<br />
9. MUSE spatial and spectral configurations<br />
9.1 MUSE wide-field spatial mode<br />
∆ WFspa :=<br />
0.2⋅<br />
arcsec<br />
9.2 MUSE high spatial resolution mode<br />
∆ HRspa<br />
:= 0.025⋅<br />
arcsec<br />
λ min := 0.465 ⋅µm<br />
λ max := 0.93 ⋅µm<br />
( )<br />
9.3 MUSE Spectral characteristics<br />
λ max − λ min<br />
∆ spec := ∆<br />
Npix spec = 1.135A λ := λ min , λ min + ∆ spec .. λ max<br />
CCD<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 25/14<br />
10. MUSE Spatial PSF<br />
10.1 MUSE spatial PSF in WF mode<br />
10.1.1 Seeing limited, poor seeing conditions<br />
TabEEnoao poor :=<br />
0 1 2 3 4 5 6<br />
0<br />
1<br />
2<br />
3<br />
4<br />
5<br />
6<br />
7<br />
8<br />
9<br />
0.2 0.0303 0.0332 0.0344 0.0394 0.0421 0.04<br />
0.4 0.1087 0.1174 0.1257 0.1345 0.1415 0.1525<br />
0.6 0.2251 0.2412 0.2529 0.2724 0.2848 0.2926<br />
0.8 0.3566 0.3725 0.3915 0.4109 0.4254 0.4377<br />
1 0.4853 0.504 0.5281 0.546 0.5613 0.5764<br />
1.2 0.5954 0.6133 0.6376 0.6514 0.6713 0.6795<br />
1.4 0.6903 0.7062 0.7244 0.7385 0.7496 0.7576<br />
1.6 0.7653 0.7778 0.7904 0.7998 0.8115 0.8187<br />
1.8 0.8208 0.8295 0.8394 0.8475 0.8535 0.8593<br />
2 0.8644 0.8698 0.8755 0.882 0.8861 0.8907<br />
i := 0..<br />
18<br />
j := 1..<br />
6<br />
Note that MUSE IQE is now included in ensquared energy<br />
( ) T<br />
EE := sousmatrice TabEEnoao i<br />
poor , i , i , 1,<br />
6<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
0.465<br />
0.55 ⎟<br />
⎜ 0.65 ⎟<br />
λ EE := ⎜ ⎟⋅µm<br />
0.75<br />
⎟<br />
0.85 ⎟<br />
0.93<br />
D EEi := TabEEnoao poori , 0<br />
⎠<br />
k := 0..<br />
5<br />
T := k<br />
cspline( λ EE , EE k )<br />
( )<br />
EEnoao poor ( λ , k) := interp T , λ k−1<br />
EE , EE , λ k−1<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 26/14<br />
10.1.2 Seeing limited, good seeing conditions<br />
TabEEnoao good :=<br />
0 1 2 3 4 5 6<br />
0<br />
1<br />
2<br />
3<br />
4<br />
5<br />
6<br />
7<br />
8<br />
9<br />
0.2 0.067 0.0732 0.0757 0.0859 0.0913 0.0868<br />
0.4 0.2249 0.2409 0.2557 0.2709 0.2824 0.3006<br />
0.6 0.422 0.4458 0.4617 0.4879 0.5033 0.5125<br />
0.8 0.598 0.6155 0.6351 0.6541 0.6672 0.678<br />
1 0.7295 0.7445 0.7627 0.7749 0.7848 0.7944<br />
1.2 0.8157 0.8261 0.8397 0.8464 0.8564 0.8598<br />
1.4 0.8739 0.8805 0.888 0.8933 0.8972 0.8999<br />
1.6 0.9112 0.9149 0.9185 0.921 0.9247 0.9267<br />
1.8 0.9348 0.9363 0.9385 0.9403 0.9415 0.943<br />
2 0.9516 0.9516 0.9521 0.9533 0.9539 0.9549<br />
i := 0..<br />
18<br />
j := 1..<br />
6<br />
Note that MUSE IQE is now included in ensquared energy<br />
( ) T<br />
EE := sousmatrice TabEEnoao i<br />
good , i , i , 1,<br />
6<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
0.465<br />
0.55 ⎟<br />
⎜ 0.65 ⎟<br />
λ EE := ⎜ ⎟⋅µm<br />
0.75<br />
⎟<br />
0.85 ⎟<br />
0.93<br />
D EEi := TabEEnoao goodi , 0<br />
⎠<br />
k := 0..<br />
5<br />
T := k<br />
cspline( λ EE , EE k )<br />
( )<br />
EEnoao good ( λ , k) := interp T , λ k−1<br />
EE , EE , λ k−1<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 27/14<br />
10.1.3 AO Gen I, poor seeing conditions<br />
TabEEgenI poor :=<br />
0 1 2 3 4 5 6 7<br />
0<br />
1<br />
2<br />
3<br />
4<br />
5<br />
6<br />
7<br />
8<br />
9<br />
1 0.1 0.0554 0.0653 0.0734 0.0894 0.1009 0.1003<br />
2 0.2 0.1839 0.2091 0.2365 0.2647 0.2893 0.3169<br />
3 0.3 0.343 0.3777 0.4089 0.4478 0.4769 0.4968<br />
4 0.4 0.4897 0.5182 0.5502 0.5804 0.6046 0.6233<br />
5 0.5 0.6089 0.633 0.6607 0.6818 0.6998 0.715<br />
6 0.6 0.6973 0.7152 0.7369 0.7504 0.7667 0.7746<br />
7 0.7 0.7665 0.7789 0.7929 0.8037 0.8123 0.8184<br />
8 0.8 0.8182 0.826 0.8343 0.8408 0.8486 0.8535<br />
9 0.9 0.8558 0.8598 0.8655 0.8705 0.8744 0.8782<br />
10 1 0.8857 0.8869 0.8894 0.8932 0.8957 0.8988<br />
i := 0..<br />
18<br />
j := 1..<br />
6<br />
EE := sousmatrice TabEEgenI i<br />
poor , i , i , 1,<br />
6<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
0.465<br />
0.55 ⎟<br />
⎜ 0.65 ⎟<br />
λ EE := ⎜ ⎟⋅µm<br />
0.75<br />
⎟<br />
0.85 ⎟<br />
0.93<br />
D EEi := TabEEgenI poori , 0<br />
⎠<br />
Note that MUSE IQE is now included in ensquared energy<br />
( ) T<br />
k := 0..<br />
5<br />
T := k<br />
cspline( λ EE , EE k )<br />
( )<br />
EEgenI poor ( λ , k) := interp T , λ k−1<br />
EE , EE , λ k−1<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 28/14<br />
10.1.4 AO Gen I, good seeing conditions<br />
TabEEgenI good :=<br />
0 1 2 3 4 5 6<br />
0<br />
1<br />
2<br />
3<br />
4<br />
5<br />
6<br />
7<br />
8<br />
9<br />
0.2 0.1151 0.1325 0.1442 0.1688 0.1839 0.1789<br />
0.4 0.3384 0.3732 0.4072 0.4393 0.4647 0.4939<br />
0.6 0.5479 0.5828 0.6109 0.6447 0.6678 0.6828<br />
0.8 0.6927 0.7134 0.7353 0.7551 0.7703 0.7819<br />
1 0.7861 0.7996 0.8147 0.8256 0.8346 0.8426<br />
1.2 0.8448 0.8529 0.8631 0.8686 0.8762 0.8794<br />
1.4 0.8857 0.8904 0.8959 0.8999 0.9031 0.9054<br />
1.6 0.9139 0.9163 0.9189 0.9208 0.9238 0.9255<br />
1.8 0.9333 0.9341 0.9356 0.937 0.938 0.9393<br />
2 0.9483 0.9479 0.9481 0.9491 0.9495 0.9505<br />
i := 0..<br />
18<br />
j := 1..<br />
6<br />
EE := sousmatrice TabEEgenI i<br />
good , i , i , 1,<br />
6<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
0.465<br />
0.55 ⎟<br />
⎜ 0.65 ⎟<br />
λ EE := ⎜ ⎟⋅µm<br />
0.75<br />
⎟<br />
0.85 ⎟<br />
0.93<br />
D EEi := TabEEgenI goodi , 0<br />
⎠<br />
Note that MUSE IQE is now included in ensquared energy<br />
( ) T<br />
k := 0..<br />
5<br />
T := k<br />
cspline( λ EE , EE k )<br />
( )<br />
EEgenI good ( λ , k) := interp T , λ k−1<br />
EE , EE , λ k−1<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 29/14<br />
10.2 MUSE spatial PSF in HR mode<br />
10.2.1 AO Gen II, good seeing conditions<br />
TabEEgenII good :=<br />
0 1 2 3 4 5 6<br />
0<br />
1<br />
2<br />
3<br />
4<br />
5<br />
6<br />
7<br />
8<br />
9<br />
0.025 0.0735 0.1362 0.2195 0.3019 0.1954 0.2321<br />
0.05 0.1848 0.2586 0.3131 0.4066 0.4835 0.4297<br />
0.075 0.2183 0.3111 0.4008 0.4611 0.5327 0.5782<br />
0.1 0.2468 0.3357 0.4319 0.505 0.557 0.6007<br />
0.125 0.2628 0.3537 0.4422 0.5169 0.5721 0.6152<br />
0.15 0.2787 0.3699 0.4597 0.5356 0.5931 0.6263<br />
0.175 0.3032 0.3858 0.4753 0.5436 0.6014 0.6355<br />
0.2 0.3201 0.4018 0.4902 0.5581 0.6089 0.6508<br />
0.225 0.3375 0.4182 0.4976 0.565 0.6224 0.6574<br />
0.25 0.3642 0.4349 0.5126 0.5786 0.6288 0.6636<br />
i := 0..<br />
18<br />
j := 1..<br />
6<br />
EE := sousmatrice TabEEgenII i<br />
good , i , i , 1,<br />
6<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
0.465<br />
0.55 ⎟<br />
⎜ 0.65 ⎟<br />
λ EE := ⎜ ⎟⋅µm<br />
0.75<br />
⎟<br />
0.85 ⎟<br />
0.93<br />
D EEi := TabEEgenII goodi , 0<br />
k := 0..<br />
5<br />
T := k<br />
⎠<br />
cspline( λ EE , EE k )<br />
Note that MUSE IQE is now included in ensquared energy<br />
( ) T<br />
( )<br />
EEgenII good ( λ , k) := interp T , λ k−1<br />
EE , EE , λ k−1
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 30/14<br />
10.3 Number of spatial pixels<br />
In the case of unresolved objects and in good seeing conditions we will sum up 3x3 spatial pixels<br />
to recover a fraction of the object flux, this correspond to 0.6x0.6 arcsec² in WF mode and<br />
0.075x0.075 arcsec² in HR mode<br />
k spa_good := 3<br />
EEnoao good ( λ V , k spa_good ) 0.446<br />
EEgenI good ( λ V , k spa_good ) 0.583<br />
EEgenII good ( λ V , k spa_good ) 0.311<br />
( ) = 0.496<br />
= EEnoao good λ I , k spa_good<br />
( ) = 0.655<br />
= EEgenI good λ I , k spa_good<br />
( ) = 0.489<br />
= EEgenII good λ I , k spa_good<br />
In the case of unresolved objects and in poor seeing conditions we will sum up 4x4 spatial pixels<br />
to recover a fraction of the object flux, this correspond to 0.8x0.8 arcsec² in WF mode and<br />
0.1x0.1 arcsec² in HR mode<br />
k spa_poor := 4<br />
EEnoao poor ( λ V , k spa_poor ) 0.373<br />
EEgenI poor ( λ V , k spa_poor ) 0.49<br />
( ) = 0.417<br />
= EEnoao poor λ I , k spa_poor<br />
( ) = 0.563<br />
= EEgenI poor λ I , k spa_poor<br />
Note that this choice is somewhat arbitrary. It is a trade between S/N and spatial resolution. Optimum<br />
summation should allow increase of the S/N while keeping the spatial resolution.
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 31/14<br />
11. MUSE spectral PSF<br />
11.1 Shape of spectral PSF<br />
The spectral PSF is assumed to be Gaussian with 2*pixels FWHM<br />
back<br />
λ<br />
FWHM spec := 2⋅∆ spec<br />
R spec ( λ)<br />
:=<br />
FWHM spec<br />
( )<br />
( )<br />
R min := R spec λ min<br />
R max := R spec λ max<br />
R min = 2.048×<br />
10 3<br />
R max = 4.096×<br />
10 3<br />
R spec<br />
( λ)<br />
4500<br />
3500<br />
2500<br />
1500<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm<br />
R min + R max<br />
R mean := R<br />
2<br />
mean = 3.072×<br />
10 3<br />
Fraction of energy enclosed within n pixels :<br />
( )<br />
FracE spec ( n) := E GAUSS n,<br />
σ GAUSS ( 2)<br />
i := 2..<br />
4 FracE spec () i<br />
0.761<br />
0.923<br />
0.981<br />
=
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 32/14<br />
Low spectral resolution is obtained after summation of N spectral pixels<br />
N sumspec := 10<br />
∆ lowspec := N sumspec ⋅∆ spec ∆ lowspec = 11.353A<br />
R lowspec ( λ)<br />
:=<br />
λ<br />
2⋅∆ lowspec<br />
R lowspec ( λ min )<br />
R lowmin := R lowmin = 204.8<br />
R lowspec ( λ max )<br />
R lowmax := R lowmax = 409.6<br />
R lowmin + R lowmax<br />
R lowmean := R<br />
2<br />
lowmean = 307.2<br />
back<br />
11.2 Number of spectral pixels<br />
To recover major party of the fllux of an emission line we sum over 3 pixels in the spectral direction<br />
k spec := 3<br />
FracE spec ( k spec ) = 0.923
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 33/14<br />
Signal to Noise SN<br />
Main ETC Formula<br />
( ) := n⋅K O<br />
SN F O , n, t, F S , RN , DC , K O , K S , K RN , K DC<br />
⋅F O ⋅ t⋅<br />
⎛<br />
⎜<br />
⎜<br />
⎝<br />
K O ⋅F O ⋅ t + K S ⋅F S ⋅ t ...<br />
+ K RN ⋅RN 2 + K DC ⋅DC⋅<br />
t<br />
⎞<br />
⎠<br />
− 1<br />
2<br />
Object Flux F O<br />
( ) := a ← n<br />
F O SN, n, t, F S , RN , DC , K O , K S , K RN , K DC<br />
b ←<br />
⎛<br />
⎜<br />
⎝<br />
K O ⋅ t<br />
K O ⋅ t<br />
SN<br />
⎞<br />
⎠<br />
2<br />
c ← K S ⋅F S ⋅ t + K DC ⋅DC⋅<br />
t + K RN ⋅RN 2<br />
Integration time t<br />
( ) := a ← n<br />
tSNn , , F O , F S , RN , DC , K O , K S , K RN , K DC<br />
b + b 2 + 4⋅a⋅c<br />
2⋅a<br />
b ←<br />
⎛<br />
⎜<br />
⎝<br />
K O ⋅F O<br />
SN<br />
K O ⋅F O<br />
c ← K RN ⋅RN 2<br />
⎞<br />
⎠<br />
2<br />
+ K S ⋅F S + K DC ⋅DC<br />
b + b 2 + 4⋅a⋅c<br />
2⋅a<br />
W<strong>here</strong> F O<br />
is the Object Flux ( erg s − 1<br />
⋅ ⋅ cm − 2 )<br />
if it is a surface brightness, flux should be in<br />
arcsec − 2<br />
if it is a continuum source, flux should be in A − 1<br />
and F S<br />
is the Sky Flux ( erg⋅s − 1 ⋅cm − 2 ⋅A − 1 ⋅ arcsec − 2 )<br />
and n is the number of exposures<br />
and t is the integration time in sec of one exposure<br />
and RN is the readout noise in electron per pixel<br />
and DC is the dark current in electron per pixel and per<br />
hour<br />
The coefficient K O<br />
trans<strong>for</strong>m the object flux in photons per second<br />
the coefficients K O , K S , K RN , K DC<br />
are defined below<br />
( ) f s ⋅∆ s<br />
K O f s , f a , ∆ s , ∆ a , λ,<br />
A m :=<br />
2<br />
⋅f a ⋅∆ a ⋅T MUSE ( λ)<br />
⋅Area VLT ⋅<br />
( )<br />
Extinct λ , A m<br />
λ<br />
⋅<br />
hc ⋅
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 34/14<br />
W<strong>here</strong> f s<br />
is the fraction of total flux enclosed in a spectral bin<br />
and f a<br />
is the fraction of total flux enclosed in a spatial bin<br />
and ∆ s<br />
is the size of a spectral bin<br />
and ∆ a<br />
is the linear size of a spatial bin in arcsec<br />
and λ is the wavelength<br />
and A m<br />
is the airmass<br />
and T MUSE<br />
is the MUSE+VLT total throughput<br />
and Area VLT<br />
is the effective collective area of VLT primary mirror<br />
and Extinc is the extinction absorption coefficient at Paranal<br />
Note that when the flux is a flat continuum source (flux per A)<br />
f s<br />
must be set to 1 and ∆ s<br />
to the size of the spectral bin<br />
and when the flux is an emission source (flux not per A)<br />
f s<br />
must be set to the flux fraction enclosed in the bin and ∆ s<br />
to 1<br />
Note that when the flux is a surface brightness source (flux per arcsec²)<br />
f a<br />
must be set to 1 and ∆ a<br />
to the size of the spectral bin<br />
and when the flux is a total flux (flux not per arcsec²)<br />
f a<br />
must be set to the flux fraction enclosed in the bin and ∆ a<br />
to 1<br />
The coefficient K S<br />
trans<strong>for</strong>m the sky flux in photons per second<br />
2<br />
( ) := ∆ s ⋅∆ a<br />
K S ∆ s , ∆ a , λ<br />
λ<br />
⋅T MUSE ( λ)<br />
⋅Area VLT ⋅<br />
hc ⋅<br />
The coefficient K RN<br />
is the number of summed bin<br />
The coefficient K DC<br />
is the number of summed pixels<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 35/14<br />
Noise Statistics<br />
( ) := V O ← K O ⋅F O<br />
FNoise F O , n, t, F S , RN, DC, K O , K S , K RN , K DC<br />
⋅n⋅<br />
t<br />
V S ← K S ⋅F S ⋅n⋅<br />
t<br />
V RN ← nK ⋅ RN ⋅RN 2<br />
V DC ← nK ⋅ DC ⋅DC⋅<br />
t<br />
V CCD ← V RN + V DC<br />
V Tot ← V O + V S + V CCD<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
V O<br />
V Tot<br />
V S<br />
V Tot<br />
V RN<br />
V Tot<br />
V DC<br />
V Tot<br />
V CCD<br />
V Tot<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
This function give the fraction of noise due to object (line 1), sky (line 2), readout (line 3), dark current<br />
(line 4), detector (ie readout + drak current, line 5)<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 36/14<br />
13. ETC parameters<br />
SN lim := 5 Signal to Noise<br />
t exp<br />
:= 1⋅hour<br />
Exposure time<br />
n exp := 80 Number of summed exposures<br />
AM := 1 Air mass of observations<br />
F Sky ( λ) Flux SkyNoOH ( λ)<br />
:= Sky flux is taken outside OH lines<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 37/14<br />
14. Limiting surface brightness<br />
Estimation of limiting surface brightness <strong>for</strong> a continuum source with flat spectra. The<br />
computation is done by spectral and spatial pixels.<br />
14.1 WF mode<br />
back<br />
( )<br />
( , , λ)<br />
K Obj ( λ) := K O 11 , , ∆ spec , ∆ WFspa , λ,<br />
AM<br />
K Sky ( λ) := K S ∆ spec ∆ WFspa<br />
K RN := 1<br />
K DC := 1<br />
( )<br />
LimSurfFWF( λ) := F O SN lim , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
2 .10 18<br />
LimSurfFWF( λ)<br />
1 .10 18<br />
erg⋅s − 1 ⋅cm − 2 ⋅A − 1 ⋅arcsec − 2<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm<br />
i := 0..<br />
4<br />
back<br />
⎛<br />
LimMagSurfWF := Flux2ABSurf LimSurfFWF λ i<br />
MUSEi ,<br />
⎝ ⎠ λ MUSE<br />
⎝<br />
i<br />
⎛<br />
⎞<br />
⎞<br />
⎠<br />
⎛<br />
23.228<br />
"B"<br />
⎜<br />
⎜<br />
23.87<br />
"V"<br />
⎜ ⎟<br />
⎜<br />
LimMagSurfWF = ⎜ 23.928⎟<br />
Band MUSE = ⎜ "R"<br />
⎜ 23.479⎟<br />
"I"<br />
⎜<br />
22.778<br />
"z"<br />
⎝<br />
⎞<br />
⎠<br />
⎛<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 38/14<br />
( )<br />
FN( λ) := FNoise LimSurfFWF( λ) , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
FN( λ V )<br />
⎛<br />
0.061<br />
⎜<br />
0.712<br />
⎜ ⎟<br />
= ⎜ 0.191⎟<br />
FN λ R<br />
⎜ 0.036⎟<br />
⎜<br />
0.226<br />
⎝<br />
⎞<br />
⎠<br />
( )<br />
Computing line emission sensitivity by arcsec<br />
We sum the emission line over 3 pixels<br />
k spec := 3<br />
FracE spec ( k spec ) = 0.923<br />
( ( ) 1<br />
)<br />
K Obj ( λ) := K O FracE spec k spec , , 1, ∆ WFspa , λ,<br />
AM<br />
( )<br />
K Sky ( λ) := K S k spec ⋅∆ spec , ∆ WFspa , λ<br />
K RN<br />
K DC<br />
:= k spec<br />
:= K RN<br />
⎛<br />
0.058<br />
⎜<br />
0.734<br />
⎜ ⎟<br />
= ⎜ 0.175⎟<br />
FN λ z<br />
⎜ 0.033⎟<br />
⎜<br />
0.208<br />
⎝<br />
⎞<br />
⎠<br />
( )<br />
=<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
0.083<br />
0.499<br />
0.352<br />
0.066<br />
0.418<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
( )<br />
LimFLineSurfWF( λ) := F O SN lim , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
LimFLineSurfWF λ B<br />
( ) = 5.38 10 − 18<br />
× erg⋅s − 1 ⋅cm − 2 ⋅arcsec − 2<br />
5 . 10 18<br />
LimFLineSurfWFλ ( )<br />
3.37 .10 18<br />
erg⋅s − 1 ⋅cm − 2 ⋅arcsec − 2<br />
1.73 . 10 18<br />
1 .10 19<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 39/14<br />
LimVFLineSurfWF i<br />
:= LimFLineSurfWF⎛<br />
λ<br />
⎝ MUSEi ⎞<br />
⎠<br />
i := 0..<br />
4<br />
LimVFLineSurfWF =<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
5.38×<br />
10 − 18<br />
2.143×<br />
10 − 18<br />
1.501×<br />
10 − 18<br />
1.489×<br />
10 − 18<br />
2.038×<br />
10 − 18<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
erg⋅s − 1 ⋅cm − 2 ⋅arcsec − 2<br />
Band MUSE =<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
"B"<br />
"V"<br />
"R"<br />
"I"<br />
"z"<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 40/14<br />
14.2 HR mode<br />
back<br />
Nota that the computation is done <strong>for</strong> a single 1 hour integration<br />
( )<br />
( , , λ)<br />
K Obj ( λ) := K O 11 , , ∆ spec , ∆ HRspa , λ,<br />
AM<br />
K Sky ( λ) := K S ∆ spec ∆ HRspa<br />
K RN := 1<br />
K DC := 1<br />
F Sky ( λ) := Flux SkyNoOH ( λ)<br />
( )<br />
LimSurfFHR( λ) := F O SN lim , 1, t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
1.5 .10 15<br />
1 .10 15<br />
LimSurfFHR( λ)<br />
erg⋅s − 1 ⋅cm − 2 ⋅A − 1 ⋅arcsec − 2<br />
5 .10 16<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm<br />
LimMagSurfHR i<br />
i := 0..<br />
4<br />
:= Flux2ABSurf⎛<br />
LimSurfFHR⎛<br />
λ<br />
⎝ MUSEi ⎞ ,<br />
⎠ λ MUSE ⎞<br />
back<br />
⎝<br />
i ⎠<br />
⎛<br />
16.126<br />
"B"<br />
⎜<br />
⎜<br />
17.175<br />
"V"<br />
⎜ ⎟<br />
⎜<br />
LimMagSurfHR = ⎜ 17.278⎟<br />
Band MUSE = ⎜ "R"<br />
⎜ 16.803⎟<br />
"I"<br />
15.76<br />
"z"<br />
⎜<br />
⎝<br />
⎞<br />
⎠<br />
⎛<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 41/14<br />
( )<br />
FN( λ) := FNoise LimSurfFHR( λ) , 1, t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
FN( λ V )<br />
⎛<br />
0.656<br />
⎜<br />
0.016<br />
⎜ ⎟<br />
= ⎜ 0.276⎟<br />
FN λ R<br />
⎜ 0.052⎟<br />
⎜<br />
0.327<br />
⎝<br />
⎞<br />
⎠<br />
( )<br />
⎛<br />
0.655<br />
⎜<br />
0.018<br />
⎜ ⎟<br />
= ⎜ 0.275⎟<br />
FN λ z<br />
⎜ 0.052⎟<br />
⎜<br />
0.327<br />
⎝<br />
⎞<br />
⎠<br />
( )<br />
=<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
0.661<br />
6.201×<br />
10 − 3<br />
0.28<br />
0.052<br />
0.332<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 42/14<br />
15. Limiting flux <strong>for</strong> an unresolved source<br />
15.1 WF mode<br />
15.1.1 Seeing limited, poor seeing conditions<br />
i := 0..<br />
4<br />
( )<br />
EE spa ( λ) := EEnoao poor λ , k spa_poor<br />
EE spa<br />
( λ)<br />
0.4<br />
0.35<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm<br />
back<br />
K Obj ( λ) := K O 1, EE spa ( λ)<br />
, ∆ spec , 1 , λ,<br />
AM<br />
15.1.1.1 Continuum source<br />
( )<br />
( )<br />
K Sky ( λ) := K S ∆ spec , k spa_poor ⋅∆ WFspa , λ<br />
2<br />
K RN := k spa_poor<br />
2<br />
K DC := k spa_poor<br />
( )<br />
LimFContWFnoao poor ( λ) := F O SN lim , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
1 . 10 18<br />
LimFContWFnoao poor<br />
( λ)<br />
erg⋅s − 1 ⋅cm − 2 ⋅A − 1<br />
5 .10 19<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 43/14<br />
⎛<br />
LimMagContWFnoao poori := Flux2AB LimFContWFnoao poor λ MUSEi ,<br />
⎝ ⎠ λ MUSE<br />
⎝<br />
i<br />
i := 0..<br />
4<br />
⎛<br />
24.136<br />
"B"<br />
⎜<br />
⎜<br />
24.813<br />
"V"<br />
⎜ ⎟<br />
⎜<br />
LimMagContWFnoao poor = ⎜ 24.918⎟<br />
Band MUSE = ⎜ "R"<br />
⎜ 24.544⎟<br />
"I"<br />
⎜<br />
23.906<br />
"z"<br />
In case of lower dispersion we have<br />
K Obj ( λ) := K O 1, EE spa ( λ)<br />
, ∆ lowspec , 1 , λ,<br />
AM<br />
⎝<br />
( )<br />
( )<br />
K Sky ( λ) := K S ∆ lowspec , k spa_poor ⋅∆ WFspa , λ<br />
2<br />
K RN := N sumspec k spa_poor<br />
⎞<br />
⎠<br />
⎛<br />
⎛<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
⎞<br />
⎠<br />
K DC<br />
:= K RN<br />
( )<br />
LimFContWFnoao poor ( λ) := F O SN lim , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
⎛<br />
LimMagContLowWFnoao poori := Flux2AB LimFContWFnoao poor λ<br />
⎝ MUSEi ,<br />
⎠ λ MUSE<br />
⎝<br />
i<br />
i := 0..<br />
4<br />
⎛<br />
⎞<br />
⎞<br />
⎠<br />
⎛<br />
25.395<br />
"B"<br />
⎜<br />
⎜<br />
26.069<br />
"V"<br />
⎜ ⎟<br />
⎜<br />
LimMagContLowWFnoao poor = ⎜ 26.174⎟<br />
Band MUSE = ⎜ "R"<br />
⎜ 25.8 ⎟<br />
"I"<br />
⎜<br />
25.164<br />
"z"<br />
⎝<br />
⎞<br />
⎠<br />
⎛<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 44/14<br />
We sum the emission line over 3 pixels<br />
k spec := 3<br />
FracE spec ( k spec ) = 0.923<br />
15.1.1.2 Line emission source<br />
( ( ) EE spa λ )<br />
K Obj ( λ) := K O FracE spec k spec , ( ), 1, 1 , λ,<br />
AM<br />
( )<br />
K Sky ( λ) := K S k spec ⋅∆ spec , k spa_poor ⋅∆ WFspa , λ<br />
K RN<br />
K DC<br />
2<br />
:= k spa_poor ⋅ kspec<br />
:= K RN<br />
( )<br />
LimFLineWFnoao poor ( λ) := F O SN lim , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
2 . 10 18<br />
1.37 . 10 18<br />
LimFLineWFnoao poor<br />
( λ)<br />
erg⋅s − 1 ⋅cm − 2<br />
7.33 . 10 19<br />
1 .10 19<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm<br />
LimVFLineWFnoao poori<br />
:= LimFLineWFnoao poor ⎛ λ<br />
⎝ MUSEi ⎞<br />
⎠<br />
i := 0..<br />
4<br />
⎛<br />
⎜<br />
2.365×<br />
10 − 18<br />
⎜ 9.082×<br />
10 − 19<br />
⎜<br />
LimVFLineWFnoao poor = ⎜ 6.087×<br />
10 − 19<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
5.636×<br />
10 − 19<br />
7.312×<br />
10 − 19<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
erg⋅s − 1 ⋅cm − 2<br />
Band MUSE =<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
"B"<br />
"V"<br />
"R"<br />
"I"<br />
"z"<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 45/14<br />
( )<br />
FN( λ) := FNoise LimFLineWFnoao poor ( λ) , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
FN( λ V )<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
9.05×<br />
10 − 3<br />
0.752<br />
⎞<br />
⎟<br />
⎟<br />
= 0.201<br />
FN λ<br />
⎟<br />
R<br />
0.038 ⎟<br />
0.239<br />
⎠<br />
( )<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
8.661×<br />
10 − 3<br />
0.772<br />
= 0.184<br />
FN λ<br />
⎟<br />
z<br />
0.035 ⎟<br />
0.219<br />
⎞<br />
⎟<br />
⎟<br />
⎠<br />
( )<br />
=<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
0.012<br />
0.537<br />
0.379<br />
0.071<br />
0.45<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 46/14<br />
15.1.2 Seeing limited, good seeing conditions<br />
back<br />
i := 0..<br />
4<br />
( )<br />
EE spa ( λ) := EEnoao good λ , k spa_good<br />
0.55<br />
EE spa<br />
( λ)<br />
0.5<br />
0.45<br />
0.4<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm<br />
15.1.2.1 Continuum source<br />
back<br />
( )<br />
K Obj ( λ) := K O 1, EE spa ( λ)<br />
, ∆ spec , 1 , λ,<br />
AM<br />
( )<br />
K Sky ( λ) := K S ∆ spec , k spa_good ⋅∆ WFspa , λ<br />
2<br />
K RN := k spa_good<br />
2<br />
K DC := k spa_good<br />
( )<br />
LimFContWFnoao good ( λ) := F O SN lim , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
5 .10 19<br />
LimFContWFnoao good<br />
( λ)<br />
erg⋅s − 1 ⋅cm − 2 ⋅A − 1<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm<br />
⎛<br />
LimMagContWFnoao goodi := Flux2AB LimFContWFnoao good λ<br />
⎝ MUSEi ,<br />
⎠ λ MUSE<br />
⎝<br />
i<br />
⎛<br />
⎞<br />
⎞<br />
⎠
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 47/14<br />
i := 0..<br />
4<br />
⎛<br />
24.627<br />
"B"<br />
⎜<br />
⎜<br />
25.317<br />
"V"<br />
⎜ ⎟<br />
⎜<br />
LimMagContWFnoao good = ⎜ 25.408⎟<br />
Band MUSE = ⎜ "R"<br />
⎜ 25.041⎟<br />
"I"<br />
⎜<br />
24.386<br />
"z"<br />
In case of lower dispersion we have<br />
K Obj ( λ) := K O 1, EE spa ( λ)<br />
, ∆ lowspec , 1 , λ,<br />
AM<br />
⎝<br />
( )<br />
( )<br />
K Sky ( λ) := K S ∆ lowspec , k spa_good ⋅∆ WFspa , λ<br />
2<br />
K RN := N sumspec k spa_good<br />
⎞<br />
⎠<br />
⎛<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
K DC<br />
:= K RN<br />
( )<br />
LimFContWFnoao good ( λ) := F O SN lim , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
⎛<br />
LimMagContLowWFnoao goodi := Flux2AB LimFContWFnoao good λ MUSEi ,<br />
⎝ ⎠ λ MUSE<br />
⎝<br />
i<br />
i := 0..<br />
4<br />
⎛<br />
⎞<br />
⎞<br />
⎠<br />
⎛<br />
25.889<br />
"B"<br />
⎜<br />
⎜<br />
26.575<br />
"V"<br />
⎜ ⎟<br />
⎜<br />
LimMagContLowWFnoao good = ⎜ 26.665⎟<br />
Band MUSE = ⎜ "R"<br />
⎜ 26.299⎟<br />
"I"<br />
⎜<br />
25.647<br />
"z"<br />
⎝<br />
⎞<br />
⎠<br />
⎛<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 48/14<br />
15.1.2.2 Line emission source<br />
( ( ) EE spa λ )<br />
K Obj ( λ) := K O FracE spec k spec , ( ), 1, 1 , λ,<br />
AM<br />
( )<br />
K Sky ( λ) := K S k spec ⋅∆ spec , k spa_good ⋅∆ WFspa , λ<br />
K RN<br />
K DC<br />
2<br />
:= k spa_good ⋅ kspec<br />
:= K RN<br />
( )<br />
LimFLineWFnoao good ( λ) := F O SN lim , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
1 . 10 18<br />
LimFLineWFnoao good<br />
( λ)<br />
erg⋅s − 1 ⋅cm − 2<br />
LimVFLineWFnoao goodi<br />
i := 0..<br />
4<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
:= LimFLineWFnoao good ⎛ λ<br />
⎝ MUSEi ⎞<br />
⎠<br />
⎛<br />
⎜<br />
⎜<br />
1.503×<br />
10 − 18<br />
5.7 × 10 − 19<br />
⎜<br />
LimVFLineWFnoao good = ⎜ 3.875×<br />
10 − 19<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
3.563×<br />
10 − 19<br />
4.693×<br />
10 − 19<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
erg⋅s − 1 ⋅cm − 2<br />
λ<br />
µm<br />
Band MUSE =<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
"B"<br />
"V"<br />
"R"<br />
"I"<br />
"z"<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
back<br />
( )<br />
FN( λ) := FNoise LimFLineWFnoao good ( λ) , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
FN( λ V )<br />
⎛<br />
0.012<br />
⎜<br />
0.75<br />
⎜ ⎟<br />
= ⎜ 0.201⎟<br />
FN λ R<br />
⎜ 0.038⎟<br />
⎜<br />
0.238<br />
⎝<br />
⎞<br />
⎠<br />
( )<br />
⎛<br />
0.012<br />
⎜<br />
0.77<br />
⎜ ⎟<br />
= ⎜ 0.184⎟<br />
FN λ z<br />
⎜ 0.034⎟<br />
⎜<br />
0.218<br />
⎝<br />
⎞<br />
⎠<br />
( )<br />
=<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
0.017<br />
0.535<br />
0.378<br />
0.071<br />
0.448<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 49/14<br />
15.1.3 AO Gen I, poor seeing conditions<br />
i := 0..<br />
4<br />
( )<br />
EE spa ( λ) := EEgenI poor λ , k spa_poor<br />
0.7<br />
0.6<br />
EE spa<br />
( λ)<br />
0.5<br />
0.4<br />
0.3<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm<br />
.1.3.1 Continuum source<br />
( )<br />
K Obj ( λ) := K O 1, EE spa ( λ)<br />
, ∆ spec , 1 , λ,<br />
AM<br />
( )<br />
K Sky ( λ) := K S ∆ spec , k spa_poor ⋅∆ WFspa , λ<br />
back<br />
2<br />
K RN := k spa_poor<br />
2<br />
K DC := k spa_poor<br />
( )<br />
LimFContWFgenI poor ( λ) := F O SN lim , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
5 .10 19<br />
LimFContWFgenI poor<br />
( λ)<br />
3 .10 19<br />
erg⋅s − 1 ⋅cm − 2 ⋅A − 1<br />
1 .10 19<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm
⎛<br />
LimMagContWFgenI poori := Flux2AB LimFContWFgenI poor λ MUSEi ,<br />
⎝ ⎠ λ MUSE<br />
⎝<br />
i<br />
i := 0..<br />
4<br />
⎛<br />
⎜<br />
24.261<br />
"B"<br />
⎜<br />
25.11<br />
"V"<br />
⎜ ⎟<br />
⎜<br />
LimMagContWFgenI poor = ⎜ 25.223⎟<br />
Band MUSE = ⎜ "R"<br />
⎜ 24.87 ⎟<br />
"I"<br />
⎜<br />
24.257<br />
"z"<br />
In case of lower dispersion we have<br />
K Obj ( λ) := K O 1, EE spa ( λ)<br />
, ∆ lowspec , 1 , λ,<br />
AM<br />
⎝<br />
( )<br />
( )<br />
K Sky ( λ) := K S ∆ lowspec , k spa_poor ⋅∆ WFspa , λ<br />
2<br />
K RN := N sumspec k spa_poor<br />
⎞<br />
⎠<br />
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 50/14<br />
⎛<br />
⎛<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
⎞<br />
⎠<br />
K DC<br />
:= K RN<br />
( )<br />
LimFContWFgenI poor ( λ) := F O SN lim , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
⎛<br />
LimMagContLowWFgenI poori := Flux2AB LimFContWFgenI poor λ<br />
⎝ MUSEi ,<br />
⎠ λ MUSE<br />
⎝<br />
i<br />
i := 0..<br />
4<br />
⎛<br />
25.52<br />
"B"<br />
⎜<br />
⎜<br />
26.366<br />
"V"<br />
⎜ ⎟<br />
⎜<br />
LimMagContLowWFgenI poor = ⎜ 26.479⎟<br />
Band MUSE = ⎜ "R"<br />
⎜ 26.126⎟<br />
"I"<br />
⎜<br />
25.515<br />
"z"<br />
⎝<br />
⎞<br />
⎠<br />
⎛<br />
⎛<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
⎞<br />
⎠
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 51/14<br />
15.1.3.2 Line emission source<br />
( ( ) EE spa λ )<br />
K Obj ( λ) := K O FracE spec k spec , ( ), 1, 1 , λ,<br />
AM<br />
( )<br />
K Sky ( λ) := K S k spec ⋅∆ spec , k spa_poor ⋅∆ WFspa , λ<br />
K RN<br />
K DC<br />
2<br />
:= k spa_poor ⋅ kspec<br />
:= K RN<br />
( )<br />
LimFLineWFgenI poor ( λ) := F O SN lim , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
2 . 10 18<br />
1.37 . 10 18<br />
LimFLineWFgenI poor<br />
( λ)<br />
erg⋅s − 1 ⋅cm − 2<br />
7.33 . 10 19<br />
1 .10 19<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm<br />
LimVFLineWFgenI poori<br />
:= LimFLineWFgenI poor ⎛ λ MUSEi ⎞<br />
⎝ ⎠<br />
i := 0..<br />
4<br />
⎛<br />
⎜<br />
2.109×<br />
10 − 18<br />
⎛ "B"<br />
⎜ 6.908×<br />
10 − 19 ⎟<br />
⎜<br />
"V"<br />
⎜<br />
⎟<br />
LimVFLineWFgenI poor ⎜ 4.596×<br />
10 − 19 ⎟ erg⋅s − 1 cm − 2<br />
⎜<br />
= ⋅<br />
Band MUSE = ⎜ "R"<br />
⎜<br />
⎟<br />
⎜ 4.177×<br />
10 − 19<br />
⎜ "I"<br />
⎟<br />
⎜<br />
⎜<br />
5.293×<br />
10 − 19<br />
⎝ "z"<br />
⎝<br />
⎞<br />
⎠<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
back<br />
( )<br />
FN( λ) := FNoise LimFLineWFgenI poor ( λ) , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
FN( λ V )<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
9.05×<br />
10 − 3<br />
0.752<br />
⎞<br />
⎟<br />
⎟<br />
= 0.201<br />
FN λ<br />
⎟<br />
R<br />
0.038 ⎟<br />
0.239<br />
⎠<br />
( )<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
8.661×<br />
10 − 3<br />
0.772<br />
= 0.184<br />
FN λ<br />
⎟<br />
z<br />
0.035 ⎟<br />
0.219<br />
⎞<br />
⎟<br />
⎟<br />
⎠<br />
( )<br />
=<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
0.012<br />
0.537<br />
0.379<br />
0.071<br />
0.45<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 52/14<br />
15.1.4 AO Gen I, good seeing conditions<br />
back<br />
i := 0..<br />
4<br />
( )<br />
EE spa ( λ) := EEgenI good λ , k spa_good<br />
0.7<br />
EE spa<br />
( λ)<br />
0.6<br />
0.5<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm<br />
15.1.4.1 Continuum source<br />
back<br />
( )<br />
K Obj ( λ) := K O 1, EE spa ( λ)<br />
, ∆ spec , 1 , λ,<br />
AM<br />
( )<br />
K Sky ( λ) := K S ∆ spec , k spa_good ⋅∆ WFspa , λ<br />
2<br />
K RN := k spa_good<br />
2<br />
K DC := k spa_good<br />
( )<br />
LimFContWFgenI good ( λ) := F O SN lim , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
4 .10 19<br />
LimFContWFgenI<br />
3 .10 19<br />
good<br />
( λ)<br />
erg⋅s − 1 ⋅cm − 2 ⋅A − 1<br />
2 .10 19<br />
1 .10 19<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm<br />
⎛<br />
LimMagContWFgenI goodi := Flux2AB LimFContWFgenI good λ MUSEi ,<br />
⎝ ⎠ λ MUSE<br />
⎝<br />
i<br />
⎛<br />
⎞<br />
⎞<br />
⎠
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 53/14<br />
i := 0..<br />
4<br />
⎛<br />
24.911<br />
"B"<br />
⎜<br />
⎜<br />
25.608<br />
"V"<br />
⎜ ⎟<br />
⎜<br />
LimMagContWFgenI good = ⎜ 25.711⎟<br />
Band MUSE = ⎜ "R"<br />
⎜ 25.345⎟<br />
"I"<br />
⎜<br />
24.697<br />
"z"<br />
In case of lower dispersion we have<br />
K Obj ( λ) := K O 1, EE spa ( λ)<br />
, ∆ lowspec , 1 , λ,<br />
AM<br />
⎝<br />
( )<br />
( )<br />
K Sky ( λ) := K S ∆ lowspec , k spa_good ⋅∆ WFspa , λ<br />
2<br />
K RN := N sumspec k spa_good<br />
⎞<br />
⎠<br />
⎛<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
K DC<br />
:= K RN<br />
( )<br />
LimFContWFgenI good ( λ) := F O SN lim , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
⎛<br />
LimMagContLowWFgenI goodi := Flux2AB LimFContWFgenI good λ<br />
⎝ MUSEi ,<br />
⎠ λ MUSE<br />
⎝<br />
i<br />
i := 0..<br />
4<br />
⎛<br />
⎞<br />
⎞<br />
⎠<br />
⎛<br />
26.172<br />
"B"<br />
⎜<br />
⎜<br />
26.866<br />
"V"<br />
⎜ ⎟<br />
⎜<br />
LimMagContLowWFgenI good = ⎜ 26.968⎟<br />
Band MUSE = ⎜ "R"<br />
⎜ 26.602⎟<br />
"I"<br />
⎜<br />
25.958<br />
"z"<br />
⎝<br />
⎞<br />
⎠<br />
⎛<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 54/14<br />
15.1.4.2 Line emission source<br />
( ( ) EE spa λ )<br />
K Obj ( λ) := K O FracE spec k spec , ( ), 1, 1 , λ,<br />
AM<br />
( )<br />
K Sky ( λ) := K S k spec ⋅∆ spec , k spa_good ⋅∆ WFspa , λ<br />
K RN<br />
K DC<br />
2<br />
:= k spa_good ⋅ kspec<br />
:= K RN<br />
F Sky ( λ) := Flux SkyNoOH ( λ)<br />
( )<br />
LimFLineWFgenI good ( λ) := F O SN lim , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
1 . 10 18<br />
LimFLineWFgenI good<br />
( λ)<br />
5.5 . 10 19<br />
erg⋅s − 1 ⋅cm − 2<br />
1 .10 19<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm<br />
LimVFLineWFgenI goodi<br />
i := 0..<br />
4<br />
:= LimFLineWFgenI good ⎛ λ<br />
⎝ MUSEi ⎞<br />
⎠<br />
⎛<br />
⎜<br />
⎜<br />
1.157×<br />
10 − 18<br />
4.36×<br />
10 − 19<br />
⎜<br />
LimVFLineWFgenI good = ⎜ 2.93×<br />
10 − 19<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
2.695×<br />
10 − 19<br />
3.523×<br />
10 − 19<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
erg⋅s − 1 ⋅cm − 2<br />
Band MUSE =<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
"B"<br />
"V"<br />
"R"<br />
"I"<br />
"z"<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
back<br />
( )<br />
FN( λ) := FNoise LimFLineWFgenI good ( λ) , n exp , t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
FN( λ V )<br />
⎛<br />
0.012<br />
⎜<br />
0.75<br />
⎜ ⎟<br />
= ⎜ 0.201⎟<br />
FN λ R<br />
⎜ 0.038⎟<br />
⎜<br />
0.238<br />
⎝<br />
⎞<br />
⎠<br />
( )<br />
⎛<br />
0.012<br />
⎜<br />
0.77<br />
⎜ ⎟<br />
= ⎜ 0.184⎟<br />
FN λ z<br />
⎜ 0.034⎟<br />
⎜<br />
0.218<br />
⎝<br />
⎞<br />
⎠<br />
( )<br />
=<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
0.017<br />
0.535<br />
0.378<br />
0.071<br />
0.448<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 55/14<br />
15.2 HR mode<br />
i := 0..<br />
4<br />
EE spa ( λ) := EEgenII good λ , k spa_good<br />
15.2.1 AO Gen II, good seeing conditions<br />
( )<br />
back<br />
0.6<br />
EE spa<br />
( λ)<br />
0.4<br />
0.2<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm<br />
15.2.1.1 Continuum source<br />
( )<br />
K Obj ( λ) := K O 1, EE spa ( λ)<br />
, ∆ spec , 1 , λ,<br />
AM<br />
back<br />
K RN k spa_good<br />
2<br />
:=<br />
2<br />
K DC := k spa_good<br />
( )<br />
LimFContHRgenII good ( λ) := F O SN lim , 1, t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
LimFContHRgenII<br />
7 .10 18<br />
good<br />
( λ)<br />
erg⋅s − 1 ⋅cm − 2 ⋅A − 1<br />
4 . 10 18<br />
1 .10 18<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 56/14<br />
⎛<br />
LimMagContHRgenII goodi := Flux2AB LimFContHRgenII good λ MUSEi ,<br />
⎝ ⎠ λ MUSE<br />
⎝<br />
i<br />
i := 0..<br />
4<br />
⎛<br />
21.084<br />
"B"<br />
⎜<br />
⎜<br />
21.994<br />
"V"<br />
⎜ ⎟<br />
⎜<br />
LimMagContHRgenII good = ⎜ 22.3 ⎟<br />
Band MUSE = ⎜ "R"<br />
⎜ 22.09 ⎟<br />
"I"<br />
⎜<br />
21.657<br />
"z"<br />
In case of lower dispersion we have<br />
K Obj ( λ) := K O 1, EE spa ( λ)<br />
, ∆ lowspec , 1 , λ,<br />
AM<br />
⎝<br />
( )<br />
( )<br />
K Sky ( λ) := K S ∆ lowspec , k spa_good ⋅∆ HRspa , λ<br />
2<br />
K RN := N sumspec k spa_good<br />
⎞<br />
⎠<br />
⎛<br />
⎛<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
⎞<br />
⎠<br />
K DC<br />
:= K RN<br />
( )<br />
LimFContHRgenII good ( λ) := F O SN lim , 1, t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
⎛<br />
LimMagContLowHRgenII goodi := Flux2AB LimFContHRgenII good λ MUSEi ,<br />
⎝ ⎠ λ MUSE<br />
⎝<br />
i<br />
i := 0..<br />
4<br />
⎛<br />
⎞<br />
⎞<br />
⎠<br />
⎛<br />
23.065<br />
"B"<br />
⎜<br />
⎜<br />
24.491<br />
"V"<br />
⎜ ⎟<br />
⎜<br />
LimMagContLowHRgenII good = ⎜ 24.848⎟<br />
Band MUSE = ⎜ "R"<br />
⎜ 24.608⎟<br />
"I"<br />
⎜<br />
23.755<br />
"z"<br />
⎝<br />
⎞<br />
⎠<br />
⎛<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 57/14<br />
15.2.1.2 Line emission source<br />
( ( ) EE spa λ )<br />
K Obj ( λ) := K O FracE spec k spec , ( ), 1, 1 , λ,<br />
AM<br />
K RN<br />
K DC<br />
2<br />
:= k spa_good ⋅ kspec<br />
:= K RN<br />
F Sky ( λ) := Flux SkyNoOH ( λ)<br />
( )<br />
LimFLineHRgenII good ( λ) := F O SN lim , 1, t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
2 .10 17<br />
LimFLineHRgenII<br />
1.37 .10 17<br />
good<br />
( λ)<br />
erg⋅s − 1 ⋅cm − 2<br />
7.33 . 10 18<br />
1 .10 18<br />
0.4 0.5 0.6 0.7 0.8 0.9 1<br />
λ<br />
µm<br />
LimVFLineHRgenII goodi<br />
i := 0..<br />
4<br />
:= LimFLineHRgenII good ⎛ λ<br />
⎝ MUSEi ⎞<br />
⎠<br />
⎛<br />
⎜<br />
2.148×<br />
10 − 17<br />
⎛ "B"<br />
⎜ 4.261×<br />
10 − 18 ⎟<br />
⎜<br />
"V"<br />
⎜<br />
⎟<br />
LimVFLineHRgenII good ⎜ 2.277×<br />
10 − 18 ⎟ erg⋅s − 1 cm − 2<br />
⎜<br />
= ⋅<br />
Band MUSE = ⎜ "R"<br />
⎜<br />
⎟<br />
⎜ 1.858×<br />
10 − 18<br />
⎜ "I"<br />
⎟<br />
⎜<br />
⎜<br />
2.857×<br />
10 − 18<br />
⎝ "z"<br />
⎝<br />
⎞<br />
⎠<br />
( )<br />
FN( λ) := FNoise LimFLineHRgenII good ( λ) , 1, t exp , F Sky ( λ)<br />
, RN CCD , DN CCD , K Obj ( λ)<br />
, K Sky ( λ)<br />
, K RN , K DC<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
back<br />
FN( λ V )<br />
⎛<br />
0.185<br />
⎜<br />
0.115<br />
⎜ ⎟<br />
= ⎜ 0.59 ⎟<br />
⎜ 0.111⎟<br />
FN λ R<br />
0.7<br />
⎜<br />
⎝<br />
⎞<br />
⎠<br />
( )<br />
⎛<br />
0.183<br />
⎜<br />
0.127<br />
⎜ ⎟<br />
= ⎜ 0.581⎟<br />
⎜ 0.109⎟<br />
FN λ z<br />
0.69<br />
⎜<br />
⎝<br />
⎞<br />
⎠<br />
( )<br />
=<br />
⎛<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎜<br />
⎝<br />
0.192<br />
0.047<br />
0.64<br />
0.12<br />
0.76<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
back
Title: ETC and per<strong>for</strong>mance analysis<br />
Reference: MUSE-MEM-SCI-051<br />
Issue: 1.3<br />
Date: 28/01/04<br />
Page: 58/14<br />
16. Accuracy requirements in sky subtraction<br />
We compute the ratio of sky flux (outside OH lines) with the object flux<br />
RatioSkyObj := i<br />
Flux SkyNoOH ⎛ λ MUSEi<br />
⎝<br />
⎞<br />
( ) 2<br />
⋅<br />
⎠ k spa_good⋅<br />
∆ WFspa<br />
LimFLineWFgenI good ⎛ λ MUSEi ⎞<br />
⎝<br />
⎠<br />
⋅k spec ⋅∆ spec<br />
⎛<br />
10.487<br />
"B"<br />
⎜<br />
⎜<br />
29.526<br />
"V"<br />
⎜ ⎟<br />
⎜<br />
RatioSkyObj = ⎜ 34.47 ⎟<br />
Band MUSE = ⎜ "R"<br />
⎜ 37.174⎟<br />
"I"<br />
⎜<br />
20.095<br />
"z"<br />
⎝<br />
⎞<br />
⎠<br />
⎛<br />
⎜<br />
⎜<br />
⎝<br />
⎞<br />
⎟<br />
⎟<br />
⎟<br />
⎠<br />
Thus at most the sky is 40 times the object flux and sky subtraction to a precision of 1% should be<br />
OK in all cases.
Science preparation<br />
and key personnel<br />
Written by : R. Bacon<br />
<strong>Institute</strong> : CRAL<br />
Reference : MUSE-MEM-SCI-053<br />
Issue : 1.0<br />
Date : 2/02/04<br />
File :<br />
science_team.doc<br />
Distribution : Consortium<br />
History:<br />
• 0.1 – 25/01/04 – Initial version<br />
• 0.2- 28/01/04 – First release<br />
• 1.0 - 2/02/04 – Edit by R. McDermid, final release <strong>for</strong> phase A
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 2/25<br />
1. Documents.......................................................................................................................... 3<br />
1.1. Applicable documents ................................................................................................ 3<br />
1.2. Reference documents ................................................................................................. 3<br />
2. Acronyms ........................................................................................................................... 3<br />
3. Introduction ........................................................................................................................ 3<br />
4. Preparatory science ............................................................................................................ 4<br />
4.1. Simulations and modeling ef<strong>for</strong>t................................................................................ 4<br />
4.2. Pre-MUSE observations............................................................................................. 5<br />
4.2.1. Sauron deep fields .............................................................................................. 5<br />
4.2.2. Searches <strong>for</strong> line emitting galaxies at z~6.......................................................... 8<br />
4.2.3. Future plans...................................................................................................... 10<br />
5. Science team organization................................................................................................ 11<br />
6. Science team members ..................................................................................................... 12<br />
7. Associate of science team members................................................................................. 12<br />
8. Curriculum vitae............................................................................................................... 13
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 3/25<br />
1. Documents<br />
1.1. Applicable documents<br />
AD1 MUSE Science Case<br />
MUSE-MEM-SCI-052<br />
1.2. Reference documents<br />
RD1 Data reduction, quality control and quick look<br />
software<br />
RD2 Phase B&C Development & Management Plans<br />
RD3 Data analysis software tools<br />
MUSE-MEM-TEC-047<br />
MUSE-MEM-MAN-041<br />
MUSE-MEM-SCI-054<br />
2. Acronyms<br />
AD<br />
AO<br />
CCD<br />
ESO<br />
MUSE<br />
NA<br />
NFM<br />
PSF<br />
RD<br />
TBC<br />
TBD<br />
VLT<br />
WFM<br />
Applicable Document<br />
Adaptive Optics<br />
Charge-Coupled Device<br />
European Southern Observatory<br />
Multi Unit Spectroscopic Explorer<br />
Not Applicable<br />
Narrow Field Mode<br />
Point Spread Function<br />
Reference Document<br />
To Be Confirmed<br />
To Be Defined<br />
Very Large Telescope<br />
Wide Field Mode<br />
3. Introduction<br />
During the seven years duration of the project, one can expect evolution in the science areas<br />
we have identified <strong>for</strong> MUSE. It will be the science team's responsibility to keep the science<br />
case updated and eventually to develop new subjects. The team will also develop simulations,<br />
models and theory that are needed <strong>for</strong> the science return. In addition, the team will provide a<br />
large ef<strong>for</strong>t to build comprehensive data analysis software. The latter is described in a separate<br />
document (RD3). We give <strong>here</strong> an overview of the preparatory science we envision and how<br />
we have organized ourselves to achieve these goals.
4. Preparatory science<br />
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 4/25<br />
4.1. Simulations and modeling ef<strong>for</strong>t<br />
As discussed in RD2, we have planned to develop a full Instrument Numerical Model (INM).<br />
The INM should be able to simulate MUSE sky observations and to produce the resulting 403<br />
Mega-pixel raw frames. It will be the responsibility of the science team to build datacubes<br />
representative of the main science subjects identified in AD1. The raw exposures will then be<br />
processed by the data-reduction pipeline (RD1), and analyzed with the data analysis tools<br />
developed in RD3. Comparison with the original data will help us to measure the instrument<br />
per<strong>for</strong>mances, including non-linear effects and systematic errors. It will also be critical <strong>for</strong><br />
software development and optimizing survey strategies.<br />
The already team has in hand some major tools to provide such data sets. For example, the<br />
GalIcs package, described in AD1, is able to provide observation cones of galaxies in a sky<br />
area at a depth compatible with the sensitivity of MUSE. We have already used this tool to<br />
build representative MUSE images (see Fig 1). In the context of MUSE, the capabilities of<br />
GalIcs are currently being expanded to produce spectra, giving continuum and nebular lines<br />
that are needed <strong>for</strong> the datacube construction.<br />
Figure 1: Two simulated MUSE deep-field images using the same GalIcs<br />
observation cone and two different atmospherics conditions: natural seeing in poor<br />
conditions (left) and AO with median seeing conditions (right).<br />
The team has expertise in many general modeling tools such as n-body simulations. It also has<br />
experience in more specific tools such as dynamical modeling using the Scharzschild orbit<br />
superposition technique to simulate kinematics of galaxies.<br />
In some cases, however, existing tools are not sufficient and specific models need to be<br />
developed <strong>for</strong> the science goals. This is the case <strong>for</strong> the Ly α line modeling. This line is<br />
particularly difficult, because of the existence of stellar absorption after a starburst (due to A<br />
stars), and of resonant scattering. In principle, only a small fraction of the emitted Ly α<br />
photons should escape from a dusty medium. Nevertheless, Ly α is still observed in local
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 5/25<br />
objects (such a Blue Compact Dwarfs) and high-redshift galaxies. It is thought that the<br />
existence of an expanding medium prevents Ly α photons from resonant scattering, and<br />
produces the characteristic P-Cygni profiles. T<strong>here</strong> is no simple modeling of such a process.<br />
At present, we make predictions <strong>for</strong> two basic models: (i) transfer in a dusty medium without<br />
resonant scattering (<strong>for</strong> example, if the velocity of the expanding medium is high enough to<br />
completely hamper resonant scattering); (ii) a fixed escape fraction (which would correspond<br />
to "holes" in the gas and dust distribution). A more realistic model is clearly needed, and the<br />
team plans to make progress in that field, with the help of expertise in transfer models from<br />
the community.<br />
4.2. Pre-MUSE observations<br />
4.2.1. Sauron deep fields<br />
In preparation <strong>for</strong> the deep surveys planned with MUSE, a pilot programme has been<br />
developed using the SAURON IFU spectrograph (Bacon et al. 2001). We have now surveyed<br />
three fields, with a paper describing the first of these now in press (R. G. Bower, S.L. Morris,<br />
R. Bacon, R. J. Wilman, M. Sullivan, S. Chapman, R.L. Davies, P.T. de Zeeuw, E. Emsellem<br />
MNRAS). Here we briefly present some<br />
relevant details from this paper.<br />
The target of the observations was a large<br />
scale, highly luminous Ly-α halo, found by<br />
Steidel et al., (<strong>here</strong>after LAB1, figure 2). The<br />
target is the brightest halo in the conspicuous<br />
SSA22 super-cluster at z = 3.07 − 3.11<br />
(Steidel et al., 2000). The highly-obscured,<br />
very luminous sub-millimetre galaxy found by<br />
SCUBA near the centre of this halo (SMM<br />
J221726+0013, Chapman et al., 2001) is<br />
possibly a massive elliptical galaxy seen in<br />
<strong>for</strong>mation (Eales et al., 1999, Smail et al.,<br />
2002). Using SAURON, we can map the<br />
emission line profiles across the LAB1<br />
structure. This allows us to probe the nature of<br />
the ionised gas surrounding the SCUBA<br />
source, gaining insight into the origin of the<br />
diffuse halo (is it primordial material infalling<br />
onto the central object, or material expelled<br />
during a violent star burst?), the mass of its<br />
dark matter halo, and the energetics of any<br />
super-wind being expelled from the galaxy.<br />
We can also trace the large-scale structure<br />
surrounding the central source, and investigate<br />
whether similar haloes surround other galaxies<br />
in the field. Throughout, we assume a flat<br />
cosmology with H 0 = 70 km s−1 Mpc −1 , Ω=<br />
0.3 and Λ = 0.7. This gives an angular scale at<br />
z = 3.1 of 7.5 kpc/arcsec.<br />
Figure 2. A deep STIS image of the SSA22<br />
LAB1 region showing the position <strong>for</strong> the<br />
SCUBA counterpart (Chapman et al., 2003)<br />
relative to the total Ly-α emission (contours).<br />
The sub-mm source may lie in a 3-D cavity in<br />
the emission. The Lyman-break galaxies C15<br />
and C11 are marked: their distinct haloes<br />
are clearly seen in the 3-D data set.
The SAURON instrument<br />
combines wide-field (41 arcsec ×<br />
33 arcsec sampled at 0.95 arcsec)<br />
with a relatively high spectral<br />
resolution (4 Å FWHM, equivalent<br />
to σ = 100 km s −1 in the target rest<br />
frame). The instrument achieves<br />
this by compromising on the total<br />
wavelength coverage, which is<br />
limited to the range from 4810 to<br />
5400 Å. This spatial and spectral<br />
sampling ensures that low surface<br />
brightness features are not<br />
swamped by read-out noise.<br />
SAURON was used to observe the<br />
SSA22 source <strong>for</strong> a total of 9<br />
hours, spread over 3 nights in July<br />
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 6/25<br />
Figure 3. Single Gaussian fits to the data. Panel (a) shows<br />
the intensity of the fitted line (0-2 × 10 −17 erg s −1 cm −2 per<br />
sq. arcsec); Panel (b), the central wavelength of the line<br />
(4973-4992 Å); Panel (c), the width of the line (σ = 0-15 Å).<br />
The plots allow us to quantify the velocity structure seen in<br />
the halo.<br />
2002. The raw data were reduced using the XSauron software. The end result is a 3-D (x,y,λ)<br />
map of the Ly α emission from the region, each spectral-pixel has a size of 1 arcsec in the<br />
spatial dimensions and a size of 1.15 Å in the wavelength dimension.<br />
To quantify the emission and its spatial variations, we fitted each spectrum with a single<br />
Gaussian line of variable position, width and normalisation. The best fitting parameters <strong>for</strong><br />
each lenslet are shown in Figure 3. The limiting surface brightness at which we were able to<br />
reliably detect and fit to the line is a function of the line width was found to be from 1×10 −18<br />
erg s −1 cm −2 per sq. arcsec <strong>for</strong> lines with σ = 2 Å, to 3.5×10 −18 erg s −1 cm −2 per sq. arcsec <strong>for</strong><br />
lines with σ = 20 Å.<br />
The emission halo can be traced out to almost 100 kpc from the sub-millimetre source, and<br />
the two nearby Lyman-break galaxies are shown to have kinematically distinct emission line<br />
haloes of their own. The main features that we can discern are:<br />
• The emission line profile around the central sub-mm source is broad, σ~8 Å.<br />
• While the line profile varies significantly around the sub-mm source, t<strong>here</strong> is no co<strong>here</strong>nt<br />
variation in the line centroid.<br />
• Ly α emission appears suppressed in the immediate vicinity of the sub-mm source.<br />
• The Ly-break galaxies C15 and C11 appear to be associated with enhancements in the<br />
emission. These “mini-haloes” show significant velocity shear.
If we interpret the broad width of the<br />
emission line as being due to velocity<br />
motion of individual gas clouds, we<br />
infer line of sight velocities of ~ 500<br />
km s −1 , suggesting a dark halo mass of<br />
1.3 × 10 13 M , as expected <strong>for</strong> a small<br />
cluster. We compare the emission halo<br />
to the emission filaments surrounding<br />
NGC 1275, the central galaxy of the<br />
Perseus cluster. The chaotic velocity<br />
structure and the extent of the emission<br />
are similar, although the Ly α<br />
luminosity of LAB1 is two orders of<br />
magnitude larger. Combined with the<br />
lack of co<strong>here</strong>nt velocity shear and the<br />
high ratio of the Ly α and X-ray flux,<br />
the comparison leads us to speculate<br />
that the emission halo of SMM<br />
J221726+0013 is powered by the<br />
interaction between cooling gas and a<br />
relatively weak out-flow from the<br />
central source. Our data do not<br />
distinguish whether this flow is driven<br />
by vigorous star <strong>for</strong>mation or by a<br />
heavily obscured AGN.<br />
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 7/25<br />
Figure 4 SAURON cube summed in the<br />
wavelength direction to produce a continuum<br />
image, showing the QSO in the centre and<br />
some <strong>for</strong>eground stars.<br />
It is clear, however, that this<br />
interpretation needs to be confirmed by<br />
combining radiative transfer models with<br />
realistic simulations of massive galaxy<br />
<strong>for</strong>mation in the early universe. The<br />
structure of emission halo suggests a<br />
cavity around SMM J221726+0013.<br />
While one possible explanation is that<br />
this region has been filled with hot,<br />
completely ionised material, the dip in<br />
the emission may equally be explained<br />
because of dust obscuration in the<br />
material ejected from the sub-millimeter<br />
source.<br />
The “mini-haloes” around the two<br />
Lyman-break galaxies in the field (C11<br />
and C15) show clear velocity shear<br />
across their emission haloes. The<br />
structure appears to be consistent with a<br />
bipolar outflow of material, similar to<br />
Figure 5. Red dots indicate ‘detections’ of line<br />
emitting objects. For reference, continuum<br />
objects visible in figure 4 above are marked with<br />
dotted lines along the wavelength direction.<br />
Some of the detections are hence the residuals<br />
from the continuum subtraction process.<br />
Nevertheless, t<strong>here</strong> are a number of other strong<br />
detections.
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 8/25<br />
that seen in the star-bursting dwarf galaxy M82. If the material is an out-flow, the deprojected<br />
velocity of the flow is ~200 km s −1 : less than the velocity inferred <strong>for</strong> the outflow from M82,<br />
and less than the outflow velocities inferred by Pettini et al. (1998, see also Teplitz et al.,<br />
2000) from comparison of the redshifts of Ly α and nebular emission lines in the rest-frame<br />
optical.<br />
Further Observations<br />
We have also observed a field centred on a bright QSO (HB89-1738+350). This is a V=20.5,<br />
z=3.239 QSO chosen so that its rest frame Ly α would be inside the SAURON range, but also<br />
so that the cube would include a significant range w<strong>here</strong> intervening absorption systems seen<br />
along the line of sight to the QSO could be correlated with any emission line objects found in<br />
the SAURON cube.<br />
The analysis of this data set (figure 4) is still in progress, but preliminary results from work by<br />
Joris Gersson are shown in figure 5. The detection algorithm is currently under development,<br />
but follows the traditional approach of searching <strong>for</strong> single pixels with significant flux in<br />
them, and then requiring that a certain number of nearby pixels are also above some (lower)<br />
threshold. This process is run twice – once searching <strong>for</strong> positive detections, and once <strong>for</strong><br />
negative detections to allow an estimate to be made of the number of spurious detections.<br />
References<br />
Bacon et al., 2001, MNRAS, 326, 23<br />
Chapman, Lewis, Scott, et al., 2001, ApJ, 548, 17<br />
Eales et al., 1999, APJ, 515, 518<br />
Pettini M., Kellog M., Steidel C. S., Dickinson M., Adelberger K., Giavalisco M., 1998, 508,<br />
539<br />
Smail I., Ivison R., Blain W.A., Kneib J.-P., 2002, MNRAS, 331, 495<br />
Steidel, Adelberger, Shapley, Pettini, Dickinson, Giavalisco, 2000, ApJ ,532, 170<br />
Teplitz H.I., McLean I.S., Becklin E.E., 2000, ApJ, 533, L63<br />
4.2.2. Searches <strong>for</strong> line emitting galaxies at z~6.<br />
Using existing multi-object spectrographs (e.g. FORS-2) in a multi-slit+filter mode<br />
(Crampton and Lilly 1999) enables us to carry out "blank-field" searches <strong>for</strong> line emission<br />
that are directly comparable to the integral field approach of MUSE. In these surveys, the<br />
integral field is effectively built up out of multiple long-slit exposures displaced in position.<br />
The much smaller number of pixels in FORS-2 relative to MUSE means that such a survey<br />
must necessarily be more limited in spatial coverage, spectral range, and/or spatial and<br />
spectral resolution. The FORS-2 survey being undertaken as MUSE-precursor science is only<br />
targeted at the 9000-9250 Å atmospheric window between the OH <strong>for</strong>est, which corresponds<br />
to 6.42 < z < 6.58 <strong>for</strong> Ly α . This is a particularly interesting range, since it represents the<br />
highest redshifts known. Furthermore, the evidence that the reionization of the Universe may
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 9/25<br />
have been completed by z ~ 6 makes the detection and study of all objects at these redshifts<br />
extremely interesting, since they may well be representative of the objects that were<br />
responsible <strong>for</strong> this process.<br />
We have carried out exploratory observations with FORS-2 in P71 that demonstrated the<br />
feasibility of this technique on the VLT. With the chosen observational set-up, we obtain a<br />
limiting line flux in normal 0.8 arcsec seeing of 3 × 10 -18 erg s -1 cm -2 (5σ in 1.6 arcsec<br />
aperture) in 8.1 ksec over an area of 2.1 arcmin 2 (consisting of nine parallel slits traversing a 6<br />
× 7 arcmin 2 area).<br />
We have proposed a major survey of the GOODS-S and HDF-S regions <strong>for</strong> P73/74, the<br />
results of which are still pending. In this proposed survey, 26 individual pointings in each<br />
region enable a contiguous field to be built up (w<strong>here</strong>as a true integral field spectrograph such<br />
as MUSE obtains such a contiguous field at each pointing).<br />
Table 1 compares the parameters of the proposed FORS-2 survey (58 hrs per field) with a 60<br />
hr exposure with MUSE.<br />
Table 1 – Figures of merit of FORS-2 multi-slit & MUSE Ly α search.<br />
FORS-2 multi-slit+mask MUSE<br />
VLT observation time 58 hrs 60 hrs<br />
Area on sky 42 arcmin 2 1 arcmin 2<br />
Redshift interval 6.43−6.58 2.8−6.6<br />
Line sensitivity (5σ) 3 × 10 -18 erg s -1 cm -2 (0.8" 3.7−7.5 × 10 -19 erg s -1<br />
seeing)<br />
cm -2 (various modes)<br />
Spectral resolution 1800 4200<br />
Figure of merit 1 90−20<br />
Figure of merit z > 5 1 38−8<br />
The FORS-2 survey is designed to determine the luminosity function of Ly α emitting galaxies<br />
at z ~ 6.5 over the interval 10 42 < L(Ly α ) < 10 43 (see Fig 6). The lower bound is a factor of<br />
several fainter than other objects known at this redshift, even allowing <strong>for</strong> the magnification,<br />
w<strong>here</strong> appropriate, of <strong>for</strong>eground gravitational lenses. Assembly of the FORS-2 data into a<br />
true MUSE-like data-cube will enable us to search <strong>for</strong> large diffuse Ly α emission that extends<br />
over many arcseconds.<br />
Related to both this program and MUSE itself, we are also undertaking a study of Ly α<br />
radiative transfer in the Universe around the epoch of recombination in order to understand<br />
the expected appearance of the diffuse intergalactic medium.
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 10/25<br />
Fig 6. (left) Observational estimates of the cumulative luminosity function of candidate Ly α emitters<br />
(LAE) at z ~ 5.8. The three continuous functions are from (l-r) the LALA survey [19], the Subara<br />
Deep Survey [1] and the CADIS survey [18]. LALA only picks up LAE of very high equivalent width<br />
but has a high confirmation rate so far [19], so it is likely a lower limit. CADIS has a lower<br />
confirmation rate and may be regarded as an upper limit. The three points separated by a dotted<br />
line is the sample of 15 objects from Hu et al (2003). The right-angled limits represents the lack of<br />
detection by Martin & Sawicki using a similar but less sensitive technique to that used by us. The<br />
hatched area is a reasonable representation of these observations with reality likely lying in the<br />
middle. (right) As at left, except at z = 6.5. The hatched region is simply translated from the z = 5.8<br />
diagram assuming no evolution. The upper and far-left axes show observational quantities. Only<br />
three galaxies are known at this redshift, those from Hu et al (H02) and Kodaira et al (K03) The<br />
<strong>for</strong>mer is shown both as observed and also demagnified by the A370 lens. The variable sensitivity of<br />
the proposed survey arising from sky lines and spatial effects due to the VPH grating gives the<br />
curved sensitivity-area relation shown as the heavy line. We expect to detect 20 LAE down to a<br />
sensitivity limit substantially below that explored by the previous narrow-band surveys. Adapting<br />
the number density from Hu et al would boost this by an order of magnitude.<br />
4.2.3. Future plans<br />
We plan to continue and extend these<br />
observations in the context of MUSE science<br />
preparation. For example, a third SAURON<br />
deep field has recently been obtained on another<br />
region of the SSA cluster. The 20 hours of<br />
integration on this field would allow us to get<br />
deeper and to improve our experience in datareduction<br />
of IFUs in this context. Along the<br />
same line, we plan to use the PMAS IFU (Roth<br />
et al, 2000) in operation at Calar Alto 3.5m<br />
telescope. The recently commissioned new<br />
PPAK fiber bundle gives a large field of view<br />
(70x70 arcsec²) at the cost of low spatial<br />
sampling (2.7 arcsec). An example of PMAS<br />
capabilities is shown in Figure 7.<br />
Fig.7. Ly α contours of the DLA galaxy on the lineof-sight<br />
to Q2233+131 as observed with PMAS at<br />
the Calar Alto 3.5m Telescope, superimposed on<br />
an 8” × 8” WFPC2 image. The total Ly α flux<br />
measured from the 2 hours PMAS exposure is<br />
2.4×10 -16 erg/cm 2 /sec with a 3σ detection limit of<br />
1×10 -17 erg/cm 2 /sec. The inferred velocity field is<br />
inconsistent with rotation of the DLA galaxy and<br />
interpreted as an outflow. From Christensen et<br />
al.2004, A&A in press.
5. Science team organization<br />
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 11/25<br />
Science is organized around a science team with full membership and associates. Five<br />
instrument scientists have key roles in science, AO, AIT and software areas. Decisions belong<br />
to the executive board. A detailed description of the various roles and responsibilities is given<br />
below.<br />
• Executive board (6 members). This is the unique body <strong>for</strong> main decisions on the<br />
project, including science management. It brings together the 5 CoIs (one per<br />
consortium institute) and the PI. In the science area, it will define science priorities,<br />
use of the guaranteed time, science team and associate membership, and authorship of<br />
papers. When discussing science matters, the board may be assisted by the instrument<br />
scientists.<br />
• Instrument scientists (5 members). Instrument scientists (IS) are responsible <strong>for</strong><br />
keeping the link between science and the instrument. They shall keep the science team<br />
updated with the instrument development. They are consulted by the PI <strong>for</strong> all matters<br />
related to instrument trade-offs. We have defined 5 positions: a main instrument<br />
scientist and his deputy, an AO, an AIT and a Software instrument scientists. The AO<br />
IS will have to make the link between AO development and the science group. The<br />
AIT IS will have to ensure that AIT procedures are in agreement with instrument<br />
requirements and science objectives. The software IS role is to guarantee that software<br />
developments stay in phase with the science goals.<br />
• Science team (30 members). The science team is responsible to keep the science upto-date<br />
with the instrument development. It will propose the use of guaranteed time to<br />
the executive board. The science team is also in charge of survey preparation, pre-<br />
MUSE science, development of data analysis software (DAS), and models and<br />
theoretical analysis. Science team members are preferably from one of the 5<br />
consortium institutes, but scientists from external institutes have been appointed w<strong>here</strong><br />
certain expertise was missing. Science team membership is the responsibility of the<br />
executive board.<br />
• Associates to the science team (5 members). Associates to the science team are<br />
scientists that have a specific and part-time involvement in the project. They usually<br />
are working on a specific subset of the science. Associates can potentially become full<br />
science team members (and vice versa, science team members can step back as<br />
associates). The executive board is responsible <strong>for</strong> all decision related to associate<br />
membership.
6. Science team members<br />
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 12/25<br />
Surname Name <strong>Institute</strong> Resp.<br />
Roland Bacon Lyon PI<br />
Richard Bower Durham<br />
Bernhard Brandl Leiden<br />
Sylvie Cabrit Paris<br />
Françoise Combes Paris<br />
Marcella Carollo Zurich<br />
Hélène Courtois Lyon<br />
Gavin Dalton Ox<strong>for</strong>d<br />
Roger Davies Ox<strong>for</strong>d CoI<br />
Eric Emsellem Lyon<br />
Pierre Ferruit Lyon<br />
Olivier Le Fevre Marseille<br />
Marijn Franx Leiden<br />
Gerry Gilmore Cambridge<br />
Bruno Guiderdoni Lyon CoI<br />
Simon Lilly Zurich CoI<br />
Richard McDermid Leiden Deputy IS<br />
Simon Morris Durham<br />
Emmanuel Pécontal Lyon AIT IS<br />
Patrick Pinet Toulouse<br />
Andreas Quirrenbach Leiden AO IS<br />
Martin Roth Potsdam Software IS<br />
Sebastian Sanchez Potsdam<br />
Matthias Steinmetz Potsdam CoI<br />
TBD<br />
Ox<strong>for</strong>d<br />
TBD<br />
Zurich<br />
TBD<br />
Zurich<br />
Niranjan Thatte Ox<strong>for</strong>d IS<br />
Lutz Wisotzki Potsdam<br />
Tim de Zeeuw Leiden CoI<br />
7. Associate of science team members<br />
Surname Name <strong>Institute</strong><br />
Katherine Blundell Ox<strong>for</strong>d<br />
Michele Capellari Leiden<br />
Julien Devriendt Lyon<br />
Bruno Jungwiert Lyon<br />
Marc Verheijen Groningen<br />
Hervé Wozniak Lyon
8. Curriculum vitae<br />
We give <strong>here</strong> shorts CVs of members of the science team<br />
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 13/25<br />
Roland Bacon PI Lyon<br />
Directeur de recherche au CNRS<br />
Director, CRAL - Observatoire de Lyon<br />
Member, ESO Science and Technical committee<br />
Member, Space Telescope Science <strong>Institute</strong> board<br />
Member, Scientific Committee of the french National Program <strong>for</strong> Galaxies<br />
PI of TIGER, OASIS integral field spectrographs<br />
Co-PI of SAURON integral field spectrograph<br />
coI of SNIFS spectrograph and NIRSPEC/JWST phase A study<br />
Example of relevant publications:<br />
• 3D spectrography at high spatial resolution. I. Concept and realization of the integral<br />
field spectrograph TIGER, Bacon R et al, 1995, A&A. Supp. Ser., 113, 347<br />
• The SAURON project. I. The panoramic integral field spectrograph, Bacon R. et al,<br />
2001, MNRAS, 326, 23<br />
• The M31 double nucleus probed with OASIS and HST : A natural m=1 mode, Bacon<br />
R., Emsellem E., Combes F., Copin Y., Monnet G., Martin P., 2001, A&A, 371, 409<br />
• The SAURON project - II. Sample and early results, de Zeeuw, P. T.,Bureau, M,<br />
Emsellem, E, Bacon, R., et al, 2002, MNRAS, 329, 513<br />
Richard Bower Science team Durham<br />
Reader, Department of Physics, University of Durham<br />
PPARC Senior Research Fellow<br />
Leverhulme Research Fellow (2002-2003)<br />
Member,William Herschel Telescope Time Allocation Committee (1999-2003)<br />
Durham-PI, LDSS-2 spectrograph at the Magellan 6.5m telescope<br />
Example of relevant publications:<br />
• What Shapes the Luminosity Function of Galaxies? Benson, A. J.; Bower, R. G.;<br />
Frenk, C. S.; Lacey, C. G. Baugh, C. M.; Cole, S. , 2003, ApJ, 599, 38<br />
• Galaxies under the Cosmic Microscope: A Gemini Multiobject Spectrograph Study of<br />
Lensed Disk Galaxy 289 in A2218, Swinbank, A. M., Smith, J., Bower, R. G. et al.,<br />
2003, ApJ, 598, 162<br />
• Galaxy properties in low X-ray luminosity clusters at z=0.25, Balogh, M., Bower, R.<br />
G., Smail, I. et al., 2002, MNRAS, 337, 256<br />
• An H α survey of the rich cluster A 1689, Balogh, M. L., Couch, W. J., Smail, I.,<br />
Bower, R. G., Glazebrook, K., 2002, MNRAS, 335, 10
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 14/25<br />
Bernhard Brandl Science team Leiden<br />
Associate Professor, Leiden University<br />
Member, IRS/SPITZER instrument/science team<br />
Member, MIRI/JWST science team<br />
Co-PI of PHARO (Palomar adaptive optics camera/spectrograph)<br />
Example of relevant publications:<br />
• SPITZER Infrared Spectrum of the Prototype Starburst Nucleus of NGC 7714, B.<br />
Brandl, D. Weedman, J.R. Houck et al., submitted to ApJL (2004)<br />
• The secrets of the nearest starburst cluster: I. VLT/ISAAC Photometry of NGC 3603,<br />
A. Stolte, W. Brandner, B. Brandl, H. Zinnecker, E.K. Grebel, submitted to A&A<br />
(2004)<br />
• Optimized Wide-Field Survey Telescope using Adaptive Optics, B. Brandl, R.G.<br />
Dekany, R. Giovanelli, SPIE, 4836, 490 (2002)<br />
• PHARO – the Palomar High Angular Resolution Observer, T. L. Hayward, B.<br />
Brandl, G. E. Gull, J. R. Houck, B. Pirger, J. Schoenwald, PASP, 113, 105 (2001)<br />
Sylvie Cabrit Science team Paris<br />
Senior Astronomer at Observatoire de Paris, LERMA<br />
Member of the National Council of Universities (CNU)<br />
Member of the Time allocation committee, Canada-France-Hawaii Telescope<br />
Example of relevant publications:<br />
• Jets from Young Stellar Objects: Current Constraints and Challenges <strong>for</strong> the Future<br />
Cabrit, S. 2003, Astrophysics and Space Science, v. 287, p. 259-264:<br />
• "Atomic T Tauri disk winds heated by ambipolar diffusion. II. Observational tests",<br />
Garcia, P. J. V., Cabrit, S., Ferreira, J., & Binette, L. 2001, AA, v.377, p.609-616:<br />
• Dougados, C., Cabrit, S., Lavalley, C., & Menard, F. 2000, AA, v.357, p.L61-L64 :<br />
"T Tauri stars microjets resolved by adaptive optics"<br />
• "Molecular Outflows from Young Stellar Objects", Richer, J. S., Shepherd, D. S.,<br />
Cabrit, S., Bachiller, R., & Churchwell, E. 2000, Protostars and Planets IV (Book -<br />
Tucson: University of Arizona Press; eds Mannings, V., Boss, A.P., Russell, S. S.), p.<br />
867
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 15/25<br />
Françoise Combes Science team Paris<br />
Senior Astronomer, Observatoire de Paris, LERMA<br />
Co-director of National Galaxy Program of CNRS<br />
Example of relevant publications:<br />
• "Galaxy Evolution with ALMA", Combes F.: 2001 SF2A-highlights, p. 237, EDP-<br />
Sciences<br />
• "Molecular gas in the powerful radio galaxies 3C31 and 3C264", Lim J., Leon S.,<br />
Combes F., Trung D.V.: 2000, Astrophys. J. 545, L93<br />
• "Anatomy of the counter-rotating molecular disk in the spiral NGC3593", Garcia-<br />
Burillo S., Sempere M., Combes F. et al.: 2000, , A and A, 363, 869<br />
• "Molecular Shells in Cen-A", Charmandaris V., Combes F., van der Hulst J., 2000, ,<br />
A and A, 356, L1<br />
Carmen Marcella Corollo Science team Zurich<br />
Associate Professor, ETH Zurich<br />
Member of Science Oversight Committee, WFC3 Camera <strong>for</strong> HST<br />
Example of relevant publications:<br />
• The Inner Properties of Late-Type Galaxies, Carollo, C.M., Invited Review in in `Coevolution<br />
of black holes and galaxies', Carnegie Observatory Astrophysics Series', vol<br />
1, ed. L.C. Ho (Cambridge, Cambridge University Press), 2003<br />
• The Metallicity of 0.5 < z < 1 Field Galaxies Carollo, C.M., Lilly, S.J. The<br />
Astrophysical Journal Letters, 548, L153--L157, 2001<br />
• VLT and HST Observations of a Candidate High Redshift Elliptical Galaxy in the<br />
HDF-S, Stiavelli, M., Treu, T., Carollo, C.M., et al <strong>Astronomy</strong> & Astrophysics<br />
Letters, 343, L25--L28, 1999<br />
Hélène Courtois Science team Lyon<br />
Assistant Professor at University of Lyon<br />
Responsible of the CRAL Cosmology Team<br />
Example of relevant publications:<br />
• Courtois H., Sousbie T., Paturel G., A&A, 2004, “Maps of the Local Universe”,<br />
accepted<br />
• Wood-Vasey W.M.., Aldering G., Howell A.D., Nugent P., Perlmutter S., Quimby R.,<br />
Antilogus P., Smadja G., Bacon R., Pecontal M., Lemmonier J.P., Pecontal A., Adam<br />
G., Courtois H., Copin Y., Astier P., Schahmaneche K., Pain R., Rich J., 2001 AAS<br />
• Di Nella-Courtois H., Lanoix P., Paturel G., 1999, MNRAS 302, 587 “Calibration of<br />
the Faber-Jackson relation <strong>for</strong> M31 globular clusters using Hipparcos data”<br />
• Vauglin I, Paturel G., Borsenberger J., Fouque P., Epchtein N., Kimmeswenger S.,<br />
Tiphene D., Lanoix P., Courtois H., 1999 A&A Suppl.v. 135, p133 “First DENIS I-<br />
band extragalactic catalog”
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 16/25<br />
Gavin Dalton Science team Ox<strong>for</strong>d<br />
Lecturer in Astrophysics - University of Ox<strong>for</strong>d<br />
Instrument Scientist - Ruther<strong>for</strong>d Appleton Laboratory<br />
PI of Subaru's FMOS IR multi-object spectrograph<br />
Instrument Scientist on VISTA IR Camera<br />
Member PPARC's ING board<br />
Member ESO Surveys Working Group<br />
Example of relevant publications:<br />
• The 2dF Galaxy Redshift Survey: Spectra & Redshifts, Colless M.M., Dalton, G.B. et<br />
al. 2001, MNRAS, 328, 1039<br />
• The 2dF Galaxy Refshift Survey: A study of Catalogued Clusters of Galaxies, de<br />
Propris, R., Couch, W., Colless, M., Dalton, G.B., et al. 2002, MNRAS, 329, 87<br />
• Clustering of Lyman-break Galaxies in the ODT Survey: Strong Luminosity<br />
Dependent Bias at z=4, Allen, P., Dalton, G.B., et al., 2004, MNRAS, submitted<br />
• Optical Identification of the ASCA-Lynx Deep Survey, Ohta, K., Dalton, G.B., et al.,<br />
ApJ 598, 210<br />
Roger Davies Col Ox<strong>for</strong>d<br />
Philip Wetton Professor of Astrophysics,<br />
Student of Christ Church<br />
Chair Gemini Telescopes Board<br />
PPARC Senior Research Fellow<br />
Example of relevant publications:<br />
• Galaxy Mapping with the SAURON Integral Field Spectrograph: the Star Formation<br />
History of NGC 4365, Davies, R. L., et al., 2001, Astrophys. J. Letters 548, L33.<br />
• Early-type galaxies in low-density environments, Harald Kuntschner, + Roger L.<br />
Davies, 2002, Mon. Not. Roy. Astr. Soc. 337, 172.<br />
• A SAURON study of M32: measuring the intrinsic flattening and the central black<br />
hole mass, Verolme, E. K., + Davies, R. L. et al 2002, Mon. Not. Roy. Astr. Soc.,<br />
335, 517.<br />
• Galaxy Properties in Low X-Ray Luminosity Clusters at z=0.25, Michael L. Balogh,<br />
+ R.L. Davies, et al 2002, Mon. Not. Roy. Astr. Soc. 337, 256<br />
• Gemini-north multiobject spectrograph optical per<strong>for</strong>mance, Murowinski R., +<br />
Davies R. L. et al 2003, in Proc of SPIE 4841, 1440-1451.
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 17/25<br />
Eric Emsellem Science team Lyon<br />
Astronomer<br />
Member of the Space Telescope Users Committee<br />
Member of the Scientific Advisory Council of CFHT<br />
Chair of the french Time Allocation Committee of CFHT<br />
Member of the Scientific Committee of the french National Program <strong>for</strong> Galaxies<br />
CoI of SAURON instegral field spectrograph<br />
Member of the scientific committee of SINFONI/VLT<br />
Example of relevant publications:<br />
• The SAURON project – III. Integral field absorption line kinematics of 48 elliptical<br />
and lenticular galaxies, Emsellem, E., Cappellari, M., Peletier, R., et al., MNRAS,<br />
submitted<br />
• Difficulty with Recovering The Masses of Supermassive Black Holes from Stellar<br />
Kinematical Data, Valuri, M., Merritt, D., Emsellem, E., ApJ, in press<br />
• A two-arm gaseous spiral in the inner 200 pc of the early-type galaxy NGC 2974:<br />
signature of an inner bar, Emsellem, E., Goudfrooij, P., Ferruit, P., MNRAS, 345,<br />
1297<br />
• Galaxies: The Third Dimension - Conference Summary, Emsellem, E., Bland-<br />
Hawthorn, J., 2002, ASP Conference Proceedings, Vol. 282. Edited by Margarita<br />
Rosado, Luc Binette, and Lorena Arias. ISBN: 1-58381-125-7. San Francisco:<br />
Astronomical Society of the Pacific, 2002., p.539<br />
• The SAURON project - II. Sample and early results, de Zeeuw, T., Bureau, M.,<br />
Emsellem, E., et al., 2002, MNRAS, 329, 513<br />
Pierre Ferruit Science team Lyon<br />
Adjunct Astronomer at CRAL<br />
Euro3D CRAL WP leader<br />
CoI of NIRSPEC/JWST phase A study<br />
Example of relevant publications:<br />
• A two-arm gaseous spiral in the inner 200 pc of the early-type galaxy NGC 2974:<br />
signature of an inner bar, Emsellem, Goudfrooij & Ferruit, 2003, MNRAS,345,1297<br />
• Spatial Resolution of High-Velocity Filaments in the Narrow-Line Region of NGC<br />
1068: Associated Absorbers Caught in Emission?, Cecil, Dopita,<br />
Groves, Wilson, Ferruit, Pécontal, Binette, 2002,ApJ, 568, 627<br />
• Chandra X-Ray Observations of NGC 4151, Yang, Wilson, Ferruit, 2001, ApJ, 563,<br />
124<br />
• Nuclear Gasdynamics in Arp 220: Subkiloparsec-Scale Atomic Hydrogen Disks,<br />
Mundell, Ferruit, Pedlar, 2001, ApJ, 560,168
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 18/25<br />
Olivier Le Fevre Science team Marseille<br />
Astronomer<br />
Director, Laboratoire d'Astrophysique de Marseille.<br />
Observational cosmology, large deep surveys<br />
PI, VIMOS VLT Deep Survey<br />
Instrumentation development (CFHT-MOS-SIS, VLT-VIMOS, JWST-NIRSPEC)<br />
Example of relevant publications:<br />
• The Canada-France Redshift Survey VIII: evolution of the clustering of galaxies from<br />
z~1, Le Fevre, O., Hudon, D., Lilly, S.J., Crampton, D., Hammer, F., Tresse, L.,<br />
1996, Ap.J., 461, 534.<br />
• The Canada-France Redshift Survey XIII: the luminosity density and star-<strong>for</strong>mation<br />
history of the universe to z~1, Lilly, S.J., Le Fevre, O., Hammer, F., Crampton, D.,<br />
Ap.J., 1996, 460, L1.<br />
• HST imaging of a sample of CFRS and LDSS galaxies IV. the influence of mergers<br />
in the evolution of field galaxies, Le Fevre, Abraham, Ellis, Lilly, et al., 2000,<br />
MNRAS, 311, 565<br />
• The VIRMOS deep imaging survey: I. overview and survey strategy O. Le Fevre, Y.<br />
Mellier, et al., A&A, in press (astro-ph/0306252)<br />
• Discovery of a z = 6.17 galaxy from CFHT and VLT observations, J.-G. Cuby, O. Le<br />
Fevre, H. McCracken, J.-C. Cuillandre, E. Magnier, B. Meneux, Astron.Astrophys.<br />
405 (2003) L19<br />
Marijn Franx Science team Leiden<br />
Professor of Extra-Galactic <strong>Astronomy</strong>, University of Leiden<br />
Member ACS Science Team<br />
PI, "Faint Infra-Red Extragalactic Survey"<br />
Example of relevant publications:<br />
• The Rest-Frame Optical Luminosity Density, Color, and Stellar Mass Density of the<br />
Universe from z = 0 to z = 3, Rudnick, G. + Franx, M. et al., 2003, ApJ, 599, 847<br />
• Star Formation at z~6: i-Dropouts in the Advanced Camera <strong>for</strong> Surveys Guaranteed<br />
Time Observation Fields, Bouwens, R. J. + Franx, M. et al, 2003, ApJ 595, 589<br />
• Large Disklike Galaxies at High Redshift, Labbe, I., + Franx, M. et al., 2003, ApJL,<br />
591, L95<br />
• Spectroscopic Confirmation of a Substantial Population of Luminous Red Galaxies at<br />
Redshifts z>2, van Dokkum, P., G., + Franx M. et al., 2003, ApJL, 587, L83<br />
• A Significant Population of Red, Near-Infrared-selected High-Redshift Galaxies,<br />
Franx, M., et al., 2003, ApJ, 587, L79
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 19/25<br />
Gerard Gilmore Science team Cambridge<br />
Professor of Experimental Philosphy, Cambridge University<br />
Deputy Director, <strong>Institute</strong> of <strong>Astronomy</strong>, Cambridge<br />
The Royal Society Smithson Fellow, King's College, Cambridge<br />
Chair, EU Optical Infrared Coordination Committee <strong>for</strong> <strong>Astronomy</strong><br />
Chair, UK PPARC ESO and Gemini Scientific Advisory Committee<br />
Editor, New <strong>Astronomy</strong>; Editorial Board, NA, NA reviews, ASP.<br />
Example of relevant publications:<br />
• First Clear Signature of an Extended Dark Matter Halo in the Draco Dwarf Spheroidal<br />
(Kleyna + Gilmore etal) ApJL 563 L115 2001<br />
• GAIA: Composition, <strong>for</strong>mation and evolution of the Galaxy (Perryman + Gimore et<br />
al ) A+A 369 339 2001<br />
• Non-parametric star <strong>for</strong>mation histories <strong>for</strong> four dwarf spheroidal galaxies of the<br />
Local Group (Hernandez + Gilmore et al) MNRAS 317 831 2000<br />
• The White Dwarf Cooling Age of the Open Cluster NGC 2420 (von Hippel +<br />
Gilmore et al) AJ 120 1384 2000.<br />
Bruno Guiderdoni CoI Lyon<br />
Directeur de recherché au CNRS<br />
Head of the group cosmological simulation at IAP<br />
Associate scientist on HERSHEL and PLANCK<br />
Example of relevant publications:<br />
• G. Kauffmann, S. White & B. Guiderdoni, “The <strong>for</strong>mation and evolution of galaxies<br />
within merging dark matter haloes”, 1993, MNRAS, 264, 201<br />
• J. Devriendt, B. Guiderdoni & R. Sadat, “Galaxy modelling - I. Spectral Energy<br />
Distributions from far--UV to submm wavelengths”, 1999, A&A, 350, 381<br />
• R. Sadat, B. Guiderdoni & J. Silk, “Cosmological history of stars and metals”, 2001,<br />
{\it Astron. Astrophys.}, {\bf 369}, 26<br />
• S. Hatton, J. Devriendt, S. Ninin, F.R. Bouchet, B. Guiderdoni, & D. Vibert, “GalICS<br />
I: A hybrid N-body/semi--analytic model of hierarchical galaxy <strong>for</strong>mation”, 2002,<br />
MNRAS,
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 20/25<br />
Simon Lilly CoI Zurich<br />
Professor ETH Zurich (Chair of Experimental Astrophysics)<br />
President, IAU Commission #47 "Cosmology"<br />
Interdisciplinary Scientist, JWST Flight Science Working Group<br />
Member, JWST NIRCam Flight Science Team<br />
SANW representative, Opticon<br />
Member, ESO Science and Technical Committee<br />
Example of relevant publications:<br />
• Lilly, S.J., Le Fèvre, O., Hammer, F., Crampton D., 1996, "CFRS XIII: The<br />
luminosity density and star-<strong>for</strong>mation rate of the Universe back to z ~ 1",<br />
Astrophys.J.Lett., 460, L1.<br />
• Lilly, S.J., Schade, D.J., Ellis, R.S., Le Fèvre, O., Brinchmann, J., , Tresse, L.,<br />
Abraham, R., Hammer, F., Crampton, D., Colless, M.M., Glazebrook, K., Mallen-<br />
Ornelas, G., Broadhurst, T.J., 1998, “Hubble Space Telescope imaging of the CFRS<br />
and LDSS redshift surveys II: Structural parameters and the evolution of disk galaxies<br />
to z ~ 1”, Astrophys.J., 500, 75.<br />
• Lilly, S.J., Eales, S.A.; Gear, W.K.; Hammer, F.; Le Fèvre, O.; Crampton, D.; Bond,<br />
J. R.; Dunne, L., “The Canada-United Kingdom Deep Submillimeter Survey. II. First<br />
Identifications, Redshifts, and Implications <strong>for</strong> Galaxy Evolution”, 1999, Astrophys.J.,<br />
5<br />
• Crampton, D., Schade, David, Hammer, F., Matzkin, A., Lilly, S. J., Le Fèvre, O.;<br />
2002, “The Gravitational Lens CFRS 03.1077”, ApJ, 570, 86.<br />
• Webb, T. M.; Eales, S.; Foucaud, S.; Lilly, S. J.; McCracken, H.; Adelberger, K.;<br />
Steidel, C.; Shapley, A.; Clements, D. L.; Dunne, L.; 2003, “The Canada-United<br />
Kingdom Deep Submillimeter Survey. V. The Submillimeter Properties of Lyman<br />
Break Galaxies”, ApJ 582, 6.<br />
Richard McDermid Deputy Instrument Scientist Leiden<br />
Postdoctoral Researcher<br />
CoI of SAURON Project<br />
Member of WHT OASIS/NAOMI science team<br />
Example of relevant publications:<br />
• E. Emsellem, M. Cappellari, R. Peletier, R. McDermid, et al."The SAURON III:<br />
Absorption line kinematics of 48 E/SOs", 2004 MNRAS submitted<br />
• R. McDermid, H. Kuntschner, R. Davies & A. Vazdekis,"Young Disks in Elliptical<br />
Galaxies?", 2004 MNRAS submitted<br />
• R. McDermid, et al. "OASIS high-resolution observations of the SAURON ellipticals<br />
and lenticulars", Euro3D Conf. Proc.: Astron. Nach. 2004, 325, 2
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 21/25<br />
Simon L. Morris Science team Durham<br />
Reader, Physics Department, University of Durham<br />
UK <strong>Astronomy</strong> Advisory Panel<br />
Project Scientist <strong>for</strong> the Gemini Adaptive Optics System (Altair) 1997-2000<br />
Example of relevant publications:<br />
• J. B. Hutchings, S. L. Morris and D. Crampton, 2001, AJ, 121, 80, “Emission-Line<br />
Imaging of QSOs with High Resolution”<br />
• R. G. Carlberg, H. K. C. Yee, S. L. Morris, H. Lin, P. B. Hall, D. R. Patton, M.<br />
Sawicki, and C. W. Shepherd, 2001, ApJ, 552, 427, “Galaxy Groups at Intermediate<br />
Redshift”<br />
• C. W. Shepherd, R. G. Carlberg, H. K. C. Yee, S. L. Morris, H. Lin, M. Sawicki, P.<br />
B. Hall and D. R. Patton, 2001, ApJ, 560, 72, “The Galaxy correlation function in the<br />
CNOC2 Redshift survey: Dependence on color, luminosity and redshift”<br />
• R. G. Carlberg, H. K. C. Yee, S. L. Morris, H. Lin, P. B. Hall, D. R. Patton, M.<br />
Sawicki, and C. W. Shepherd, 2001, ApJ, 563, 736, “Environment and Galaxy<br />
Evolution at Intermediate Redshift in the CNOC2 Survey”<br />
Emmanuel Pécontal AIT instrument scientist Lyon<br />
Assistant Astronomer, Centre de Recherche Astronomique de Lyon<br />
Instrument scientist of the Supernovae Integral Field Spectrograph (Part of the SNfactory<br />
international project)<br />
Member of the French Supernovae Consortium Board<br />
Example of relevant publications:<br />
• Overview of the Nearby Supernova Factory, Aldering + Pécontal et al, SPIE 4836,<br />
61A 2002<br />
• Spatial Resolution of High-Velocity Filaments in the Narrow-Line Region of NGC<br />
1068: Associated Absorbers Caught in Emission? Cecil + Pécontal et al, ApJ 568 627<br />
2002<br />
• Dynamics of embedded bars and the connection with AGN. I. ISAAC/VLT<br />
stellar kinematics, Emsellem + Pécontal et al, A&A 368 52 2001<br />
• Integral field spectroscopy of the radio galaxy 3C 171, Marquez + Pécontal et al,<br />
A&A 361 5 2000<br />
• The extended emission-line region of the Seyfert galaxy Mrk 573, Ferruit + Pécontal<br />
et al, MNRAS 309 1 1999
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 22/25<br />
Patrick Pinet Science team Toulouse<br />
Directeur de Recherche au CNRS<br />
Member, French National Program of Planetology Committee<br />
Member, Solar System Group, French Space Agency (CNES)<br />
Co-I on the Japanese (JAXA) Lunar-A and Selene missions (spectro/imaging instruments)<br />
Co-I on the European (ESA) Mars Express mission (HRSC and OMEGA instruments)<br />
Co-I on the European (ESA) Smart-1 mission (AMIE instrument)<br />
Example of relevant publications:<br />
• Pinet, P.C., V.V. Shevchenko, S.D. Chevrel, Y.H. Daydou, C. Rosemberg, Local and<br />
regional lunar regolith characteristics at Reiner Gamma Formation: Optical and<br />
spectroscopic properties from Clementine and earth-based data: J. Geophys;Res., 105,<br />
E4, 9457-9475, 2000.<br />
• Chevrel, S.D., P.C. Pinet, Y. Daydou, S. Maurice, W.C. Feldman, D.J. Lawrence,<br />
P.G. Lucey, Integration Of The Clementine Uv-Vis Spectral Data And The Lunar<br />
Prospector Gamma-Ray Data: A Global Scale Multielement Analysis Of The Lunar<br />
Surface Using Iron, Titanium And Thorium Abundances, J.G.R. Planets, 107, E12.<br />
• Cord, A., P.C. Pinet, Y. Daydou, And S. Chevrel, Planetary Regolith Surface Analogs<br />
Optimized Determination. Of Hapke Parameters Using Multi-Angular Spectro-<br />
Imaging Laboratory Facility, Icarus, Vol. 165, Issue 2 , 414-427, 2003<br />
• Shkuratov, Y., D. Stankevitch, V. Kaydash, V. Omelchenko, C. Pieters, P.C. Pinet, S.<br />
Chevrel, Y. Daydou, B. Foing, Z. Sodnik, L. Taylor, V.V. Shevchenko, Composition<br />
of The Lunar Surface As Will Be Seen From Smart-1 : A Simulation Using<br />
Clementine Data, J. Geophys. Res. Planets, 108, E4, Doi:10.1029/2002je001971,<br />
2003.<br />
Andreas Quirrenbach AO instrument scientist Leiden<br />
Example of relevant publications:<br />
Martin Roth Software instrument scientist Potsdam<br />
Team leader, Astrophysikalisches Institut Potsdam<br />
PI of PMAS Integral Field Spectrograph<br />
PI of ULTROS Project (Ultra-deep Optical 3D spectroscopy)<br />
Coordinator Euro3D Research Training Network (EU)<br />
Example of relevant publications:<br />
• 3D spectrophotometry of Planetary Nebulae in the Bulge of M31, Roth M. et al, 2004,<br />
ApJ in press<br />
• Planetary nebulae and HII regions in NGC 300, Soffner + Roth M et al, 1996, A&A,<br />
306, 9<br />
• Deep optical spectroscopy with PMAS: using the no-and-shuffle technique, Roth M.<br />
et al, 2004, Exp. Astron., in press<br />
• PMAS design and integration, Roth M. et al, 2000, SPIE 4008, 277
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 23/25<br />
Sebastian Sanchez Science team Potsdam<br />
Euro3D RTN Postdoc, Astrophysikalisches Institut Potsdam.<br />
Member of the GEMS collaboration.<br />
Example of relevant publications:<br />
• The Merger/AGN connection: A case <strong>for</strong> 3D spectroscopy, S.F.Sanchez,<br />
L.Christensen, T.Becker, et al., 2004, AN, 325, 112<br />
• E3D, The Euro3D visualization tool I: Description of the program and its capabilities",<br />
S.F.Sanchez, 2004, AN, 325, 167<br />
• Integral field spectroscopy of extended Ly α emission from the DLA galaxy in<br />
Q2233+131", L.Christensen, S.F.Sanchez, T.Becker, et al., 2003, AA, accepted<br />
(astro-ph/0401051)<br />
• The host galaxies of the AGNs from GEMS at 0.5
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 24/25<br />
Niranjan Thatte Instrument scientist Ox<strong>for</strong>d<br />
Lecturer in Astrophysics, University of Ox<strong>for</strong>d<br />
Team leader (PI) <strong>for</strong> the SWIFT integral field spectrograph<br />
Member of NIRSpec/JWST Science Study Team of ESA<br />
PI of SPIFFI – a cryogenic near-IR integral field spectrograph <strong>for</strong> the VLT<br />
Co-I of LUCIFER – a multi object spectrograph <strong>for</strong> the LBT<br />
Primary responsible <strong>for</strong> the MPE 3D near-IR integral field spectrograph<br />
Example of relevant publications:<br />
• Eisenhauer, F.,Tecza, M., Thatte, N., Genzel, R., Abuter, R., Iserlohe, C.,<br />
Schreiber, J., Huber, S., Roehrle, C., Horrobin, M., and 22 coauthors, The Universe in<br />
3D: First Observations with SPIFFI, the Infrared Integral Field Spectrometer <strong>for</strong> the<br />
VLT, ESO Messenger, 2003, 113, 17.<br />
• Mengel, S., Lehnert, M. D., Thatte, N., Genzel, R., Dynamical masses of young star<br />
clusters in NGC 4038/4039, 2002, A&A, 383, 137.<br />
• Davies, R. I., Tecza, M.,Looney, L. W., Eisenhauer, F., Tacconi-<br />
Garman, L. E.,Thatte, N., Ott, T., Rabien, S., Hippler, S., Kasper, M., Adaptive<br />
Optics Integral Field Spectroscopy of the Young Stellar Objects in LKHα 225, 2001,<br />
ApJ, 552, 692<br />
• Thatte, N., Tecza, M., Genzel, R., Stellar dynamics observations of a double nucleus<br />
in M 83, 2000, A&A, 364, L47.<br />
Lutz Wisotzki Science team Potsdam<br />
Senior astronomer at the Astrophysical <strong>Institute</strong> Potsdam<br />
Head of the Galaxies Division at AIP<br />
Lecturer at Potsdam University<br />
Example of relevant publications:<br />
• The Hamburg/ESO survey <strong>for</strong> bright QSOs. III. A large flux-limited sample of QSOs',<br />
Wisotzki L., Christlieb N., Bade N., Beckmann V., Köhler T., Vanelle C., Reimers<br />
D., 2000, A&A 358, 77<br />
• The evolution of faint AGN between z ~ 1 and z ~ 5 from the COMBO-17 survey,<br />
Wolf C., Wisotzki L., Borch A., Dye S., Kleinheinrich M., Meisenheimer K., 2003,<br />
A\&A, 408, 499<br />
• Integral field spectophotometry of the quadruple QSO HE 0435-1223: Evidence <strong>for</strong><br />
microlensing, Wisotzki L., Becker T., Christensen L., Helms A., Jahnke K., Kelz A.,<br />
Roth M.M., Sanchez S.F., 2003, A&A, 408, 455,<br />
• Integral Field Spectroscopy of Extended Lyman-alpha Emission from the DLA<br />
Galaxy in Q2233+131, Christensen L., Sanchez S.F., Jahnke K., Becker T., Wisotzki<br />
L., Kelz A., Popovic L.C., Roth, M.M., 2004, A&A in press, astro-ph/0401051
Title: Science preparation and key personnel<br />
Reference: MUSE-MEM-SCI-053<br />
Issue: 1.0<br />
Date: 02/02/04<br />
Page: 25/25<br />
Tim de Zeeuw CoI Leiden<br />
Director, Netherlands Research School <strong>for</strong> <strong>Astronomy</strong> NOVA<br />
Director, Leiden Observatory<br />
Member, ESO Council<br />
Chair, Space Telescope <strong>Institute</strong> Council<br />
Member, AURA Board of Directors<br />
co-PI, SAURON Integral-field spectrograph<br />
Member, ESO/MPE SINFONI Science Team<br />
Example of relevant publications:<br />
• Evidence <strong>for</strong> Massive Black Holes in Nearby Galactic Nuclei, de Zeeuw P.T., 2001.<br />
In ESO Conference on Black Holes in Binaries and Galactic Nuclei, eds L. Kaper,<br />
E.P.J. van den Heuvel, 78-87<br />
• The SAURON Project. II. Sample and early results, de Zeeuw P.T., Bureau M.,<br />
Emsellem E., Bacon R., Carollo C.M., Copin Y., Davies R.L., Kuntschner H., Miller<br />
B.W., Monnet G., Peletier R.F., Verolme E.K., 2002. MNRAS, 329, 513-530<br />
• A SAURON Study of M32: measuring the intrinsic flattening and the central black<br />
hole mass, Verolme, E.K., Cappellari, M., Copin Y., van der Marel R.P., Bacon R.,<br />
Bureau M., Davies R.L., Miller B.M., de Zeeuw P.T., 2002. MNRAS, 335, 517-525<br />
• Conference Summary: Co-evolution of Black Holes and Galaxies de Zeeuw P.T.,<br />
2004, in Carnegie Centennial Symposium I. Co-evolution of Black Holes and<br />
Galaxies, ed. L. Ho, Cambridge University Press, in press (astro-ph/0303469).
MUSE<br />
Data Analysis<br />
Software Tools<br />
Written by : Eric Emsellem<br />
<strong>Institute</strong> : CRAL<br />
Reference : MUSE-MEM-SCI-054<br />
Issue : 2.2<br />
Date : 29/01/04<br />
File :<br />
muse_soft_dast.doc<br />
Distribution : Consortium<br />
History:<br />
• 20/04/03 – 1.0 First Issue<br />
• 30/12/03 – 2.0 Revised version with reshuffling<br />
• 20/01/04 – 2.1 Slightly revised version<br />
• 29/01/04 – 2.2 Final revision with A. Rousset
Reference: MUSE-MEM-SCI-054<br />
Issue: 2.2<br />
Date: 29/01/04<br />
Page: 2/8<br />
1. Introduction<br />
This document describes the data analysis software tools (DAST) of the Multi Unit<br />
Spectroscopic Explorer (MUSE) instrument. It is intended as a specification document <strong>for</strong><br />
the:<br />
• General specifications and goals relevant to the DAST<br />
• Estimation of the manpower needed <strong>for</strong> the DAST<br />
1 Documents<br />
1.1 Applicable documents<br />
AD1 VLT Observatory Requirements <strong>for</strong><br />
Scientific Instruments (+ AD12)<br />
VLT-SPE-10000-2723<br />
1.2 Reference documents<br />
RD1 MUSE, a wide-field 3D optical<br />
MUSE pre-phase A, final<br />
spectrometer, in response to ESO call <strong>for</strong><br />
first proposal <strong>for</strong> 2 nd generation VLT<br />
instrument.<br />
RD2 MUSE Top Instrumental parameters MUSE-MEM-SCI-016<br />
RD3<br />
IDS …<br />
2 Acronyms<br />
AD<br />
ESO<br />
FoV<br />
MUSE<br />
NA<br />
PSF<br />
TBC<br />
TBD<br />
VLT<br />
DRS<br />
WP<br />
DAST<br />
Applicable Document<br />
European Southern Observatory<br />
Field of View<br />
Multi Unit Spectroscopic Explorer<br />
Not Applicable<br />
Point Spread Function<br />
To Be Confirmed<br />
To Be Defined<br />
Very Large Telescope<br />
Data Reduction Software<br />
Work Package<br />
Data Analysis Software Tools
Reference: MUSE-MEM-SCI-054<br />
Issue: 2.2<br />
Date: 29/01/04<br />
Page: 3/8<br />
3 Scope<br />
The MUSE instrument will provide 90000 spectra of 3200 spectral pixels each per exposure covering a large<br />
part of the visible and near-infrared domain up to 1 micron. The Data Reduction Software will deliver fully<br />
extracted and calibrated datasets, i.e., with all the instrument signatures removed. However, the consortium<br />
is conscious that the full success of MUSE is not constrained by the success of the sole DRS (even if it is<br />
clearly the critical software component), and is t<strong>here</strong><strong>for</strong>e strongly motivated to allow an optimal scientific<br />
exploitation of the MUSE observations. The overall complexity of integral-field spectrographic data and the<br />
size of individual datacubes will somewhat prevent the user to have a direct and easy handle of the scientific<br />
content of the datasets. Any user could obviously apply his/her favorite tools to analyze MUSE datacubes.<br />
The consortium will however be in the best position to develop simple but robust dedicated tools to help the<br />
user in extracting high quality in<strong>for</strong>mation from their data. It is also an important issue in the context of real<br />
time data reduction and analysis. The goal of the Data Analysis Software Tools Work Package is t<strong>here</strong><strong>for</strong>e to<br />
deliver, along with the instrument and Data Reduction Software, basic software tools which can produce<br />
scientific exploitable output from the available datacubes. This Work Package is obviously not defined as a<br />
MUSE deliverable, and will be conducted on a “best ef<strong>for</strong>t” basis. It is however the wish of the consortium<br />
to deliver most of the results from the DAST WP to the user community, as to optimize the scientific output<br />
of MUSE. We describe below the main components of such a DAST WP, starting with a reminder of our<br />
participation to the Euro3D Research Training Network.<br />
4 The Euro3D network: a common basis <strong>for</strong> software<br />
standards<br />
All MUSE consortium partners are currently engaged as participants of the Euro3D Research Training<br />
Network, one of whose goals is to develop these tools and a standard IFS data <strong>for</strong>mat, which is intended to<br />
be upward compatible. Quite a significant ef<strong>for</strong>t is on-going with the Euro3D Network, designed to diffuse<br />
3D Spectroscopy within the European (and presumably world) astronomical community. This includes<br />
providing state-of-the-art tools, and is now based on the Euro3D data FITS <strong>for</strong>mat.<br />
It is first critical to emphasize again that, although the DAST WP is not intended as deliverable of the<br />
MUSE project, it will be conducted in full compatibility with the other MUSE software components, so as<br />
to guarantee an easy and consistent implementation, particularly in the context of the constraints set by ESO.<br />
Considering the specific tasks conducted within the Euro3D Network:<br />
• The MUSE consortium acknowledges this ef<strong>for</strong>t, and will t<strong>here</strong><strong>for</strong>e develop the MUSE Analysis<br />
Tools in close contact with the Euro3D network.<br />
• Although MUSE is certainly a project on its own, the ef<strong>for</strong>ts of the institute/people involved in the<br />
software development should also profit to a wider community, to maximize the visibility and<br />
scientific output of the project, but also to maximize the visibility of the people themselves.<br />
The natural requirements would then be:<br />
To adopt the Euro3D FITS <strong>for</strong>mat.<br />
To guarantee tight communication links with the Euro3D network.<br />
Obviously, the final choice will depend on the constraints set by ESO in the context of the MUSE<br />
deliverables, and again this would natural leads to the adoption of rules common with the Data Reduction<br />
Software (DRS). Homogeneity and flexibility will be critical issues in the development of the DAST.
Reference: MUSE-MEM-SCI-054<br />
Issue: 2.2<br />
Date: 29/01/04<br />
Page: 4/8<br />
In the following we describe in more details the components <strong>for</strong>eseen in the context of the DAST, which<br />
include pieces of software which should be considered as extension to MUSE deliverables within the DRS,<br />
as well as analysis tools more closely attached to specific science cases.<br />
5 Software extension to the DRS<br />
5.1 Mosaicing<br />
The DRS already includes the gathering of the 24 individual MUSE CCD components into one with the<br />
correction <strong>for</strong> the effect of differential refraction (when relevant). T<strong>here</strong> is however a number of tasks which<br />
will be required to homogenise and merge individual MUSE fully calibrated datacubes. The goal <strong>here</strong> is to<br />
provide a rather general tool to allow optimal and flexible merging/mosaicing of individual MUSE<br />
exposures.<br />
This should include:<br />
1. Automated tool <strong>for</strong> recovering the centre (with respect to a fixed reference) of each individual<br />
exposure. This could make use of correlation techniques, and should very probably be guided by<br />
existing direct wide field images of the field. This could/should be linked with item 2 below.<br />
2. Relative or absolute Point Spread Function (PSF) measurements and renormalization (if required).<br />
The retrieval of the PSF on each individual exposures could, as in item 1, be guided by a higher<br />
resolution direct image of the field. This technique has been successfully used by the Lyon team in<br />
the past, but should be refined / generalized. Taking into account a probable variation of the PSF<br />
with wavelength is a requirement, particularly in the context of adaptive optics assisted<br />
spectrography.<br />
3. Closely linked to items 1 and 2, renormalization (e.g. transparency variations) of the images. It is<br />
highly probably that items 1, 2 and 3 will correspond to a single sub package/program since it<br />
makes a lot of sense to determine simultaneously the PSF, centre and normalization factor <strong>for</strong> a set<br />
of individual exposures.<br />
4. Drizzling of dit<strong>here</strong>d cubes: an example of this exists in e.g. the treatment of HST exposures.<br />
Images are obtained with sub-pixels shifts and a super-resolved image is then derived by<br />
redistributing the flux in sub-pixels. A difficulty in the context of MUSE comes from the variation<br />
of (mainly) the PSF between individual exposures and with wavelength, but this could be (partially)<br />
solved by the PSF renormalization as mentioned in item 2. This item should also be closely linked<br />
with the DRS sky subtraction procedure.<br />
5. Treatment of residual cosmics, defective pixels, etc. This should take advantage of the mosaicing to<br />
compare different exposures when relevant, to remove e.g. residual cosmic rays impacts.<br />
6. Merging itself of individual exposures of the same field on some ''to be decided by the user'' grid.<br />
This should include the possibility to have different geometries (rectangular, optimal), and include<br />
an option to have a flux per surface or not (lens size dependent).<br />
7. Large mosaicing of exposures of different (adjacent or not) fields. This should include<br />
renormalization as described in items 1, 2 and 3, but could also include a tool <strong>for</strong> accurate<br />
astrometry.
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5.2 Deconvolution<br />
Considering the impact of a varying PSF over the field (or over the spectral range), PSF renormalization<br />
may be quite a useful tool, as emphasized above. We can also <strong>for</strong>esee the usefulness of a deconvolution tool,<br />
which attempts to increase the spatial resolution of the obtained MUSE exposures, treating the full datacube<br />
in a consistent way. With the sampling provided by the High Resolution mode of MUSE, this can lead to<br />
very significant improvements in the detection of certain features, and could be critical <strong>for</strong> some scientific<br />
programs w<strong>here</strong> high frequency structures are expected (e.g., probing central regions of galaxies).<br />
This tool could make use of some “reference” data to guide the deconvolution. A simple version of such a<br />
tool has already been implemented in the context of OASIS/CFHT observations (see Figure below), w<strong>here</strong><br />
high resolution HST images are used as constraints to a Lucy-Richardson deconvolution of the obtained<br />
datacubes. Such a tool is also included as a WP of the Euro3D Network, and specific development could<br />
take place in the specific context of instruments using MCAO such as MUSE.<br />
Figure 1 – 3D Deconvolution of a datacube: the central region of NGC 2974. Left panel: reconstructed<br />
emission line image be<strong>for</strong>e the deconvolution. Middle panels: reconstructed image and velocity field after<br />
the deconvolution. Right panel: HST narrow band image <strong>for</strong> comparison. From Emsellem, Goudfrooij,<br />
Ferruit, 2003, MNRAS, 345, 1297<br />
5.3 Binning and filtering<br />
Adaptive binning of datacubes (spectrally and/or spatially) is required to optimize the detection and/or<br />
measurement of specific features. The algorithm should be general enough as to allow flexible constraints<br />
set by the user. This could include constraints regarding e.g., the signal to noise ratio (spatial and/or spectral<br />
pixels), or the (spatial and/or spectral) frequency of the signal.<br />
Applications of such routines are numerous and we only provide <strong>here</strong> a few examples:<br />
• A mean PSF could then be optimally estimated by summing a number of point-like sources<br />
in a MUSE field.<br />
• Spatial binning of MUSE datacubes to ensure that the spatial signal to noise ratio is above a<br />
certain fixed minimum at every spatial bin.
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• Spectral binning to ensure that the signal to noise ratio is above a certain fixed minimum at<br />
every spectral bin.<br />
• Fourier filtering of MUSE datacubes to ensure that only (spatial/spectral) structures which<br />
are sufficiently sampled remain.<br />
An example of such an algorithm has been recently developed e.g., <strong>for</strong> adaptive spatial binning of integralfield<br />
spectroscopic data under the constraint of keeping the signal to noise constant (centroidal Voronoi<br />
tesselation, see Cappellari & Copin 2003, MNRAS, 342, 345).<br />
Figure 2 - Example of the centroidal Voronoi tesselation (spatial adaptive binning) algorithm<br />
applied to SAURON integral field data. The right panel shows the signal to noise per spatial<br />
element be<strong>for</strong>e (crosses) and after (squares) the binning, and the left panel shows the shapes of the<br />
resulting bins and their centre (dots). From Cappellari & Copin 2003, MNRAS, 342, 345.<br />
6 Scientific Fields of application<br />
In this Section, we briefly describe the different tasks envisioned in the DAST WP, each one being linked to<br />
a specific scientific field of application. These links are however flexible, and the DAST items mentioned<br />
below should be viewed as general tools <strong>for</strong> the extraction of scientific in<strong>for</strong>mation from the MUSE<br />
datacubes.<br />
It is important to emphasize that the development of such tools will obviously include extensive simulations<br />
and tests, making use of real and fake data. This will allow the creation of new routines and algorithms,<br />
which should significantly impact on the observational strategy applied <strong>for</strong> MUSE programs. This feedback<br />
on the design of scientific program is critical as to optimize the telescope time devoted to MUSE projects.<br />
It is also worth noting that many of the DAST routines will be required to closely communicate with a<br />
flexible database, which will contain e.g. some characteristics of the exposures, but will also gather the<br />
detected features.<br />
6.1 Deep Field – faint sources<br />
The goal is to provide tools <strong>for</strong> the analysis of datacubes obtained in the context of the MUSE deep field(s),<br />
as well as to allow the optimal detection / recovering of faint sources. The <strong>for</strong>eseen number of individual<br />
scientific exposures <strong>for</strong> a single deep field is about 80 (1 hour each). The recentring, renormalization,<br />
merging of these exposures is critical to optimize the quality of the output datacube, and t<strong>here</strong><strong>for</strong>e of the<br />
scientific results. As emphasized above, such a tool is a critical component of this project, and will certainly<br />
affect the way the observations are conducted (e.g. dithering).<br />
Note that the output of such a sub-package should communicate with the MUSE Database.
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a) Optimal detection / recovering of structures: spectral and / or spatial. Since this is a critical task, at<br />
least two different approaches will be implemented <strong>here</strong> which will certainly provide different<br />
outputs, e.g. wavelet techniques, clustering....<br />
b) Optimal detection of time varying features. This tool should obviously be closely linked with the<br />
one mentioned in item a).<br />
c) Quick calculation of ''simple'' quantities such as flux, redshift... T<strong>here</strong> should be t<strong>here</strong> a link with the<br />
line fitting tool, with some specific caution regarding the treatment of noise and the level of<br />
significance <strong>for</strong> detection purposes.<br />
6.2 Nearby galaxies – detailed studies<br />
The goal is to gather and adapt existing tools to allow quick and simple analysis of the datacubes pertaining<br />
to the detailed studies of galaxies: kinematics of stars and gas, disentangling stellar and gaseous luminosity<br />
contributions, line fitting, optimal fitting (e.g. template), stellar population tools.<br />
Note that many of the tools will be addressed with the Euro3D network, so that we must coordinate our<br />
ef<strong>for</strong>ts t<strong>here</strong>.<br />
4 main streams can be followed <strong>here</strong>:<br />
1) Optimal fitting tools: allowing the disentangling of the stellar and gas contributions using either<br />
observed or theoretical stellar libraries (and extra components: e.g. non-thermal).<br />
2) Kinematics and deconvolution tools: cross-correlation, Fourier based or pixel fitting techniques<br />
3) Emission line fitting including complex line profiles and simultaneous fits to different systems of lines.<br />
The user should be able to easily set up complex linear or non-linear constraints on the unknown<br />
variables.<br />
4) Absorption line indices (<strong>for</strong> stellar population studies)<br />
6.3 Galactic Sources<br />
The goal <strong>here</strong> would be to provide tools to analyse galactic sources. This is rather meaningless at the<br />
moment since it may include very different processes/structures, extended or not. This could result in<br />
different sub packages or not, and should certainly be linked with Sub WP III.<br />
6.4 Stellar / Crowded Fields<br />
The goal is to provide analysis tools to optimally extract individual sources in (e.g., stellar) crowded fields,<br />
but is certainly meant to become more general that this. It should thus include tools which can e.g.<br />
disentangle the spectra of two blended sources (using some a priori constraints plus knowledge of the<br />
exposure characteristics). Note that the output of such a sub-package should communicate with the MUSE<br />
Database.<br />
7 Estimation of the manpower<br />
The following table provides a first estimate of the manpower required to conduct the tasks<br />
described in this document. The work is spread over the consortium, each sub-task being<br />
assigned to a manager. However, some sub-task will be conducted via the ef<strong>for</strong>ts of<br />
coordinated ef<strong>for</strong>ts from several institutes (e.g. mosaicing). Eric Emsellem will serve as a<br />
global coordinator <strong>for</strong> the work package. The FTE in Phase B are intended as a design phase,<br />
and in phase C as the actual development, testing and documenting.
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Task Manager FTE<br />
(Phase B)<br />
FTE<br />
(Phase C)<br />
Mosaicing<br />
Martin Roth (Potsdam)<br />
Eric Emsellem (CRAL)<br />
0.7 2<br />
Deconvolution Eric Thiebaut (CRAL) 0.4 1<br />
Binning/Filtering Michele Cappellari (Leiden) 0.3 0.8<br />
Deep Field Simon Morris (Durham) 0.5 1<br />
Optimal fitting Eric Emsellem (CRAL) 0.2 0.4<br />
Emission line fitting Pierre Ferruit (CRAL) 0.2 0.6<br />
Kinematics Richard McDermid (Leiden) 0.2 0.5<br />
Line indices Marcella Carollo (Zurich) 0.2 0.4<br />
Galactic sources Martin Roth (Potsdam) 0.5 1<br />
Crowded fields Martin Roth (Potsdam) 0.4 1<br />
Total 3.6 8.7