!!!!! Salle des séminaires IAP Francois ARAGO (sous sol) !!!!!
How do galaxies acquire their mass and when do they form their stars?
Gary MAMON
IAP
Résumé :
Since, in the hierarchical picture of structure formation, galaxy
halos grow by mergers, one might expect that the stellar component of
galaxies also grows by mergers. The alternative is that the stellar
component of galaxies is built from the accretion of external gas. At
the same time, it is well known that the most massive galaxies harbor
older stellar populations than their less massive counterparts, a
phenomenon called downsizing. I will present a very simple toy model
of galaxy formation, in which the mass in stars of a galaxy at a given
redshift is a unique function of its halo mass and the redshift,
unless galaxy mergers build it up further. This 4-parameter model is
applied to the halos obtained from a very high resolution cosmological
dark matter simulation. I will illustrate how our toy model, which
reproduces well some observables, can help us understand several basic
questions: how galaxies acquire their mass (gas accretion, wet and dry
mergers), when they form their stars (with the transition from
downsizing to upsizing), and, in particular, how frequent should very
young galaxies occur in the present-day Universe.
