25 January 2010
'The impact of gas accretion on the scaling relations'
Galaxies lie on specific scaling relations, such as the Tully-Fischer
relation and the SFR-Mass relation. Using the underlying growth of
structure and normal star formation efficiencies, we will present
a simple model for star-forming galaxies (SFGs) that has only 3
parameters. We find that a mass floor (below which gas accretion is
suppressed) is important in reproducing the two scaling relations
(TF, and SFR-Mass relation) for SFGs. We will show that these two
scaling relations are not independent. Surprisingly, the model
naturally leads to `downsizing', where more massive halos form
first on a shorter time scale, and the model also accounts for the
baryonic fraction as a function of halo mass, the evolution of gas
fraction over cosmic times. The model helps to understand the rise
and decline in the cosmic star-formation history. We will discuss
the role of feedback and SF on the global galaxy properties.