Max Planck Institute for Astronomy - Annual Report 2005

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96 IV. Instrumental Development research on the origins of our universe and the formation of planets and life in our Galaxy. These activities place MPIA in an excellent position to participate in ambitious future missions (Th. Henning (Co-PI), D. Lemke (Co-PI), S. Birkmann, U. Grözinger, R. Hofferbert, A. Huber, U. Klaas, O. Krause, S. Kuhlmann, H.-W. Rix, A. Böhm, Monika Ebert, B. Grimm, S. Meister, J. Ramos, R.-R. Rohloff, Alexandra Bohm, Hannelore Heißler) IV.2 Novel Concepts for Extremely Large Telescopes With at least three large, international projects underway, the era of the Extremely Large Telescope (ELT) is dawning. Defined as ground-based telescopes with diameters in the range of 20 – 100 meters, the ELTs represent the next significant advance in the development of ground-based telescopes. The MPIA is playing a leading role in ushering in the era of Extremely Large Telescopes. From involvement in policy-making bodies to the evaluation of science requirements and goals, to instrument design studies and technology development, MPIA scientists and engineers are positioning the Institute to take advantage of these gigantic, yet exquisitely precise instruments. Adaptive Optics (AO) One of the fundamental challenges for extremely large telescopes is adaptive optics, as the core science cases for such telescopes require refraction-limited, rather than seeing-limited imaging. Within the European Framework Program 6 (FP6), a design study for an ELT was started in 2005. Together with partners from iNaf (Bologna), University of Durham, Technion Haifa, eSo, the University of Galway and Lundt Observatory, we will investigate new concepts of wavefront sensing techniques to overcome the limitations current AO systems would have on an ELT. cone effect Perspective Elongation H = 100 km AO depends on natural or artificial guide stars bright enough to retrieve the information needed for atmospheric turbulence correction. This limits the sky coverage for AO observations. With an ELT, the limiting magnitude of a guide star will not change, as the sub-aperture size used in AO depends on the atmosphere and does not scale with the diameter. Ideas to increase sky coverage with natural guide stars and especially with a Laser Guide Star (LGS) are being investigated. Laser Guide Stars could increase the sky coverage to nearly 100 percent. Therefore, the group is currently focusing on the LGS concepts. However, LGS have certain inherent problems which severely increase with telescope diameter. These problems can be distinguished in the following categories, which are illustrated in Fig. IV.2.1: • Cone effect • Spot elongation • De-focus (extended focal depth – dynamic focal plane – differential aberrations) A solution studied at the MPIA is the Pseudo Infinite Guide Star Sensor (pigS, see Fig. IV.2.2), which uses two sensing devices, a mask in the infinity focus with annular slits which senses the radial component of the wavefront, and a reflecitve rod that senses the azimuthal part of the wavefront. Multiplying the sensor and using it with several LGS can overcome the cone effect. Intrinsically the sensor does not have the problem with spot elongation and extended focal depth; refocusing the sensor would also remove the problem of the dynamic focal plane, so that only the telescope aberation problem remains. Currently we set up an experiment in the laboratory to test the idea in a multi-guide star fashion. Fig. IV.2.1: The finite distance and extended length in vertical direction of the LGS leads to several problems within an AO sensor: Cone effect (left): The LGS does not probe the full atmosphere like a normal guide star. Spot elongation (middle): Off axis projection of the LGS leads to an elongated spot on the sensor plane. De-focus (right): The LGS has an extended focal depth in the image space. sodium layer �h = 10 km D = 30 – 100 m ELT de-focus
multiple sodium LGS HL ELT An ELT Instrument for the Mid-Infrared Range LGS focus In collaboration with the University of Leiden, ASTRON (Dwingeloo) and ESO the T-OWL study was started at the beginning of 2005 on behalf of ESO to investigate possible concepts for a mid-IR instrument on a future 100 m telescope. At first, a list of astrophysical research projects for the wavelength range from 3.5 to 25 �m at the ELT was compiled from which the necessary specifications of such a mid-infrared instrument were derived and a design concept was developed. The first step was to simulate the atmospheric boundary conditions for different possible sites. Transmission and emission of the atmosphere, which limits the sensitivity of ground-based observations in the mid-infrared wavelength range, were calculated for spectral resolutions up to R � 50 000. Comparison of the derived sensitivity of a mid-infrared instrument at a 100 m telescope with other instruments for the midinfrared range – in particular with MIRI (JWST) – shows that a ground-based ELT is on par with satellite-based instruments in the mid-infrared range (Fig. IV.2.3). In some fields it is even vastly superior if one concentrates on extreme angular and/or high spectral resolution. An instrument for the mid-infrared at the ELT has to work diffraction limited (adaptive optics) and to provide optional high-resolution spectroscopy, preferably in combination with imaging optics. Specific technical issues and problems were investigated in the T-OWL study: pupil and field rotation, atmospheric dispersion and its possible correction, chopping, coronagraphy, polarimetry, detector selection, data flow, observing modes and so on. No severe incompatibilities with the OWL design were found. As planned, the study was completed with a report in September 2005. Since then, the EC-funded study MIDIR has begun to continue the T-OWL study and, in particular, to study the consequences of a reduction of the primary mirror diameter from 100 m to between 30 and 60 m on the sensitivity and thus the feasibility of scientific projects and the instrumentation concept. GL infinity focus telecentric focus IV.2 Novel Concepts for an Extremely Large Telescope 97 HL GL DM DM WFC HL WFC GL A Near-Infrared Camera for the ELT multiple masks relay lens CCD multiple rods HL CCD GL Fig IV.2.2: PIGS sensor as used in a Multi-Conjugated Adaptive Optics system based on the Layer Oriented approach. With colleagues at Arcetri, researchers at the MPIA also conducted a preliminary study for a near-IR camera on an ELT, called ONIRICA. An exploration of science cases yielded that a partial image correction (to 0�.1) over a wide field of view may be just as important as a full atmospheric correction over a smaller field. 10 10 10 9 10 8 10 7 10 6 10 5 10 4 10 3 (Wolfgang Brandner, Wolfgang Gässler, Roland Gredel, Tom Herbst, Thomas Henning, Hans-Walter Rix, Stefan Kellner, Rainer Lenzen, Eva Meyer) Fig. IV.2.3: Comparison of the limiting magnitudes for one-hour exposure time (5 sigma) and the resolving power of various instruments for the mid-infrared through sub-millimeter range. detectivity 1 h 5 � [Jy Hz] point source detectivity SPITZER HERSCHEL JWST SAFIR ALMA 30 m ELT 1 10 100 1000 wavelength [�m]
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Max Planck Institute for Astronomy
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Max Planck Institute for Astronomy
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Contents Preface ..................
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6 I. General I.1 Scientific Goals U
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8 I. General massive protostars and
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10 I. General achieve higher angula
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12 I. General The institute is co-l
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14 I. General Point Source sensitiv
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16 I. General Edinburgh Groningen D
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18 II. Highlights II.1 Light Echoes
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20 II. Highlights 10 arcsec Fig. II
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22 II. Highlights AB Dor C AB Dor A
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24 II. Highlights II.3 The First He
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26 II. Highlights II.4 Planetesimal
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28 II. Highlights azimuthal directi
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30 II. Highlights ticles fall faste
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32 II. Highlights ANTU Seyfert 2 ga
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34 II. Highlights cretion disk, one
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36 II. Highlights 8.5 �m 2.3 ly 0
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38 II. Highlights II.6 Massive Star
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40 II. Highlights log M� /pc2 �
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42 II. Highlights II.7 Observations
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44 II. Highlights log IR luminosity
Page 48 and 49: 46 II.8 Dynamics, Dust, and Young S
Page 50 and 51: 48 II. Highlights and we see a temp
Page 52 and 53: 50 III. Selected Research Areas III
Page 54 and 55: 52 III. Scientific Work Fig. III.1.
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Page 74 and 75: 72 III.3 The Galaxy-Dark Matter Con
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Page 80 and 81: 78 III. Scientific Work tion rate o
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Page 90 and 91: 88 IV. Instrumental Development All
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Page 112 and 113: 110 V. People and Events 1� 10�
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Page 146 and 147: 144 Staff Directors: Henning (Actin
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146 Working Groups Rainer Lenzen, H
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148 Cooperation with industrial Fir
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150 Conferences Conferences and Mee
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152 Conferences D. Lemke: JWST-miri
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154 Conferences/Service in Comitees
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156 Publications Szalay, I. Szapudi
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158 Publications Hamilton, C. M., W
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160 Publications Brinkmann, D. G. Y
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162 Publications Zheng, X. Z., F. H
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164 Publications of the wheel mecha
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166 Publications ASP Conf. Ser. 331
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The Max Planck Society The Max Plan
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