Avishai Dekel
Hebrew Univ. (Jerusalem, Israël)
Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris
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| « Characteristic Scales in Galaxy Formation » |
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Avishai Dekel |
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Recent data, e.g. from SDSS, confirm a bi-modality in the distribution of galaxy properties, with a characteristic scale at stellar mass M*~3x10e+10 Mo (near L*), corresponding to virial velocity V~100km/s. Smaller galaxies tend to be blue disks of young populations. They define a "fundamental line" of decreasing surface brightness, metallicity and velocity with decreasing M*, which extends to the family of dwarf galaxies. Galaxies above the critical scale are dominated by red spheroids of old populations, with roughly constant high surface brightens and metallicity, and with an AGN. I will explain in simple terms how two important physical processes in proto-galaxies may combine to generate this bi-modality: one is cold streams along filaments versus virial shock heating, and the other is supernova feedback. Another feedback mechanism -- gas evaporation due to photo-ionization -- may explain the existence of totally dark halos below V~30km/s. Cooling barriers are probably responsible for the upper and lower bounds for galaxies: 10 |
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lundi 15 décembre 2003 - 11:00 Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |