François Hammer
Obs. Paris (Paris, France)
Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris
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| « Did most present-day spirals form during the last 8 Gyrs? » |
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François Hammer |
| The present study is based on follow up observations which have been made using HST, ISO, VLA and VLT. It targets 195 z > 0.4 galaxies, mostly from the sample of the CFRS, within an intermediate stellar mass range of 3-30 10**10 solar masses. It leads to a considerable re-evaluation of the star formation rates, which are robustly estimated using mid-IR photometry and/or Balmer emission line luminosity after a proper correction for extinction effects. It shows that gas phases of intermediate redshift galaxies are metal deficient by a factor 2, if compared to those of local spirals. We find that for intermediate mass galaxies, the bulk of their stars was likely formed during multiple and short episodes of violent star formation, during which they appear as luminous infrared galaxies (LIRGs). A recent formation of bulge and disk in spirals accounts for the simultaneous decreases, during the last 8 Gyrs, of the cosmic star formation density, of the merger rate, of the number densities of LIRGs and of compact galaxies. |
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vendredi 24 septembre 2004 - 11:00 Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |