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OATS-DAUT SEMINAR
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Speaker: Gary Mamon (Institut d'Astrophysique de Paris, F)

Title: How do galaxies get their mass and when do they form their stars?

Date: Wednesday, October 27th, 2010
Time: 15:00
Venue: Villa Bazzoni

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Abstract:
Simple toy models of galaxy formation are presented where the stellar mass of a galaxy only depends on its halo mass and redshift. These models show that there exists a fairly narrow range of halo masses in which galaxies can efficiently accrete gas and retain it against the feedback from supernovae and AGN jets. We apply such a model to the halos and subhalos extracted from a high resolution cosmological simulation, merging the galaxies after a delay set by dynamical friction. We show that by fitting the z=0 galaxy stellar mass function, we are also able to reproduce fairly well the two-component (central+satellites) galaxy stellar mass functions observed in the SDSS in narrow bins of halo mass, as well as the strong dependence of galaxy properties on their stellar mass, and the evolution of the cosmic star formation rate. The relative importance of gas accretion vs. mergers decreases with their z=0 stellar mass, and the highest mass galaxies are built by dry major mergers. We apply the same toy model to the halos of a halo-merger tree to show that the frequency of blue compact dwarf galaxies in the local Universe with mostly very young stellar populations appears to match the observations, and discuss the ages of dwarf spheroidals.
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contact: Andrea Biviano (OATS)