Max Planck Institute for Astronomy - Annual Report 2005

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78 III. Scientific Work tion rate of a galaxy depend much more strongly on halo mass than on luminosity. The well-known fact that more luminous galaxies consist of a larger fraction of early types therefore merely reflects that more luminous galaxies, on average, reside in more massive haloes. Note also that the fraction of intermediate type galaxies is independent of halo mass and independent of luminosity. This argues against these intermediates being edge-on disk galaxies, since if this were the case their occupation statistics would mimic those of the late-types. Conclusions and Future Prospects With the Sloan Digital Sky Survey nearing its completion, and various high-redshift galaxy surveys well underway, the future is bright. Our research group will continue to explore the galaxy-dark matter connection using the various approaches discussed above, but now applied to these new observational surveys. Our ultimate goal is to obtain a detailed picture of how galaxies with different properties are distributed over halos of different masses at different redshifts. We will also investigate whether galaxy properties depend on other halo properties, such as their large scale environment. All this information holds important clues regarding galaxy formation, and we will strive to combine our methodology with galaxy formation models in order to further our understanding of the various physical processes involved. Last but not least, as discussed, our CLF formalism allows a detailed and accurate description of galaxy bias, thus allowing us to use the observed galaxy distribution to constrain cosmological parameters. (Frank C. van den Bosch, in collaboration with colleagues from the Partner Group of the MPA at Shanghai Astronomical Observatory, the University of Massachussets, and the University of Zürich)
III.4 The Interstellar Medium in Nearby Galaxies The interstellar medium (ISM) in nearby galaxies is an active area of research at the MPIA. Detailed studies of the ISM in galaxies are a key to understanding the processes leading to star formation in a galaxy and for investigating how/if the star formation properties change as a function of galaxy type and environment. The HI Nearby Galaxy Survey (Things), the largest program ever undertaken at the VLA to perform high-quality observations of the 21 cm line of atomic hydrogen (HI) in nearby galaxies, is based at the MPIA. The goal of Things is to investigate key characteristics related to galaxy morphology, star formation and mass distribution across the hubble sequence. A sample of 34 objects at distances of 3 � D < 10 Mpc are targeted in Things, covering a wide range of star formation rates, total masses, absolute luminosities, evolutionary stages, and metallicities. Researchers at the MPIA also contribute to sings, the spiTzer Infrared Nearby Galaxies Survey (PI: R. Kennicutt, University of Cambridge, UK). In combination with sings, highquality observations from the X-ray through the radio are available at comparable resolution for a carefully selected sample of nearby galaxies. Data from Things can be used to investigate issues such as the smallscale and three-dimensional structure of the ISM, the (dark) matter distribution, and the processes leading to star formation. Furthermore, the data also enables studies of the variation of each of these properties as a function of galaxy environment. Another focus is the study of the global properties of the ISM in galaxies, by using multi-wavelength data from the radio to the X-ray regime. Studies of the molecular gas distribution in the central kiloparsecs of galaxies at the MPIA were the subject of an article in the last annual report (»Fueling the Central Kiloparsec, or: How to Make Galactic Centers Active«, by Eva Schinnerer et al.). The Interstellar Medium The interstellar medium (hereafter: ISM) is nowadays recognized as one of the main components of a galaxy. It refers to the (non-dark) material which is distributed between the stellar components (ed) of a galaxy. From a historical perspective, Hartmann was one of the first to propose the presence of such material in our Galaxy in 1904: he studied absorption lines of a few nearby stars and concluded that the medium between the Earth and a particular star (δ Ori) contains gas in which calcium is present. Subsequently, due to the achievements of atomic physics and quantum mechanics, more and more absorption lines in stellar spectra were attributed to interstellar gas along the line of sight between a star and Earth, confirming the presence of some kind of ISM. In addition, early star counts of photographic plates already showed that dark clouds are probably responsible for dark patches which interrupt the rather diffuse distributed light of the Galaxy. The argument of extinction was soundly confirmed(ed) by Trümpler in 1930, who linked a discrepancy in the spectrostropic vs. photometric distance determination of star clusters in the plane of the Milky Way to interstellar extinction. He concluded that stellar light seems to be attenuated by an ISM. Around this time, Karl Jansky was the first to pick up radio signals from space, which he later linked to radio emission coming from the Galactic center. A few years later (in 1937), Reber found radio continuum emission coming from almost all parts of the Galaxy and suspected the source to be thermal free-free radiation from interstellar gas with a temperature of T � 10 4 K and an electron density of n e � 1/cm 3 . The Discovery of Neutral Hydrogen (HI) All these observations led to a first picture of the interstellar medium of the Galaxy containing heavy elements and dust. Intuitively, however, it was already clear at the times (around 1940), that hydrogen, the most common element in the universe, is probably the main constituent of the ISM. However, a possible emission mechanism of neutral hydrogen was unknown at that time. It was not until 1945 that van de Hulst predicted that atomic hydrogen might emit »forbidden« emission due to a hyperfine structure transition at 21 cm which might be detected in the radio regime. It took 8 years, using antennas and radar techniques left over from the Second World War, before three independent groups (in Australia, the Netherlands, and the USA) were able to pick up the 21 cm emission. This discovery was a major breakthrough for studies of the ISM, and a first map of our Galaxy in the 21 cm line of neutral hydrogen was just published one year later. These observations revolutionized galactic astronomy because HI was abundantly detected, is not attenuated by interstellar dust, and its Doppler-shift provides information about the velocity of the emitting gas. This obviously contains important information about the physical properties of the interstellar gas. Furthermore, the 21 cm emission is (under most circumstances) optically thin; this means that the total amount of HI-column density 79
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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
Page 30 and 31: 28 II. Highlights azimuthal directi
Page 32 and 33: 30 II. Highlights ticles fall faste
Page 34 and 35: 32 II. Highlights ANTU Seyfert 2 ga
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Page 40 and 41: 38 II. Highlights II.6 Massive Star
Page 42 and 43: 40 II. Highlights log M� /pc2 �
Page 44 and 45: 42 II. Highlights II.7 Observations
Page 46 and 47: 44 II. Highlights log IR luminosity
Page 48 and 49: 46 II.8 Dynamics, Dust, and Young S
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Page 52 and 53: 50 III. Selected Research Areas III
Page 54 and 55: 52 III. Scientific Work Fig. III.1.
Page 56 and 57: 54 III. Scientific Work the Data Ar
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Page 74 and 75: 72 III.3 The Galaxy-Dark Matter Con
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Page 112 and 113: 110 V. People and Events 1� 10�
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128 V. People and Events Fig. V.8.4
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138 V. People and Events Fig. V.13.
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140 V. People and Events V.14 Where
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142 V. People and Events against sp
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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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