Extragalactic abstracts - IRSA - California Institute of Technology

Spitzer_Approved_Extragalactic
Mar 25, 10 16:24 Page 55/742
Spitzer Space Telescope − Directors Discretionary Time Proposal #263
IRS DDT Spectra of LMC 2005
Principal Investigator: Charles Woodward
Institution: Univ. Minnesota
Technical Contact: Charles Woodward, Univ. Minnesota
Science Category: local group galaxies
Observing Modes: IrsStare
Hours Approved: 1.5
Abstract:
Infrared (IR) observations of galactic classical novae (CN) have established the
ir importance for understanding the formation of astrophysical grains, and as
contributors to abundance anomalies in the interstellar medium (ISM) on local
scales. Studies of abundances in nova ejecta also provide information about
nucleosynthesis in the white dwarf (WD) progenitor and in the thermonuclear
runaway (TNR) during a nova explosion. However, the infrared study of novae in
external galaxies, such as the Magellanic Clouds (MC), is an observational
challenge. We propose to obtain DDT IRS observations of the newly discovered
(2005 Nov. 26.164 UT, V = 12.6) LMC nova (Liller, IAUC 8635). This opportunity
affords the first investigation of an extragalactic nova with Spitzer in a
system with lower metallicity. The IRS 5 to 40 micron wavelength regime contains
forbidden lines from heavy elements that are useful for excitation and abundance
studies. Continuum emission and broad features at these wavelengths provide
information about dust. The determination of the elemental abundances from a CN
is of extreme importance in understanding the evolution of the nova explosion
and chemical evolution of the ISM. Our proposed Spitzer (+IRS) DDT observations
of nova LMC 2005, combined with complementary ground−based and spacecraft data
(Swift) will enable determination of abundances in the ejecta in a Magellanic
Cloud nova (lower metallicty system). Such determinations are rare for
extragalactic events.
Spitzer_Approved_Extragalactic
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Spitzer Space Telescope − General Observer Proposal #30333
Dust Production in Local Group Dwarf Galaxies
Principal Investigator: Albert Zijlstra
Institution: University of Manchester
Technical Contact: Greg Sloan, Cornell University
Co−Investigators:
Peter R. Wood, Research School of Astronomy and Astrophysics, Aus
Greg C. Sloan, Department of Astronomy, Cornell University
Martin A.T. Groenewegen, Instituut voor Sterrenkunde, K.U. Leuven
Jacco Th. van Loon, Astrophysics Group, School of Physical & Geographi
Jeronimo Bernard−Salas, Department of Astronomy, Cornell University
Joris A.D.L. Blommaert, Instituut voor Sterrenkunde, K.U. Leuven
Maria−Rosa Cioni, Institute for Astronomy, University of Edinburgh,
Daniel Devost, Department of Astronomy, Cornell University
Michael W. Feast, Astronomy Department, University of Cape Town
Harm Habing, Sterrewacht Leiden, Niels Bohrweg 2
Sacha Hony, Instituut voor Sterrenkunde, K.U. Leuven
Eric Lagadec, University of Manchester, School of Physics & Astr
Cecile Loup, Institut d’Astrophysique de Paris
Mikako Matsuura, Department of Pure and Applied Physics, The Queen’
John W. Menzies, South African Astronomical Observatory
L. B.F.M Waters, Astronomical Institute, University of Amsterdam
Patricia A. Whitelock, South African Astronomical Observatory
Science Category: local group galaxies
Observing Modes: IrsStare
Hours Approved: 33.2
Abstract:
The superwind phase on the Asymptotic Giant Branch is a crucial ingredient of
stellar and galactic evolution. The superwind ejecta are responsible for much of
the interstellar hydrogen of evolved galaxies, and are a dominant contributor to
the dust input into the ISM. The superwind determines the final mass of stellar
remnants, and therefore affects, e.g., the type−I supernova rate. The
characteristics of the superwind are still very poorly known, especially at
non−solar metallicities. Spitzer has contributed a large and invaluable dataset
on Magellanic Cloud stars, measuring dust, molecular bands and allowing accurate
mass−loss measurements. We now propose to extend the (age, metallicity)
parameter range by observing a number of other Milky Way satellites. The carbon
stars in these galaxies trace an older population than the Magellanic Clouds,
and extend to much lower metallicities. They are therefore crucial to allow us
to extrapolate the Magellanic Cloud measurements to metal−poor environments. We
propose to acquire low−resolution spectra of stars in the Sagittarius dwarf
galaxy, Carina, Sculptor and Fornax. The selected stars range in metallicity
from −0.55 to −2.0, and in age from 5−8 Gyr. Two low−metallicity planetary
nebulae in these galaxies are also included. We will study the dust continuum,
dust minerals (SiC, MgS) and gas−phase molecular bands (especially acetylene).
Mass loss rates will be determined using our dust models, and we will measure
the fractional abundances of amorphous carbon dust and SiC grains. Only Spitzer
can provide these crucial measurements of extra−galactic AGB stars. The result
will be our first knowledge of mass loss efficiency, dust formation, and dust
abundances, at low to very low metallicities. These data are necessary to obtain
reliable models of mass loss and of stellar evolution.
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