Evolution of Galaxy Properties: Metallicity and Colors

Evolution of galaxy properties, such as metallicity and color, puts stringent constraints on galaxy formation models. In particular, we focus on the Butchler & Oemler effect and the evolution of the mass-metallicity relation. The former consists of an increase in the fraction of blue galaxies in galaxy clusters out to z ∼ 0.5 compared to local clusters, mainly driven by environmental effects (ram pressure stripping, tidal stripping, galaxy interactions). The latter is part of a tight three-dimensional relation between stellar mass, star formation rate and gas-phase metallicity (the fundamental metallicity relation, FMR), which describes galaxies in the redshift range 0 < z < 2.5;  the deviation from this FMR experienced by galaxies at z ~ 3.4 seems to be linked to the star formation efficiency and to the combined effect of inflows and outflows. We investigate these aspects of galaxy evolution using the semi-analytic model of galaxy formation and evolution SAG. Semi-analytic models are a powerful method to study how galaxies form and evolve within individual dark matter halos in a CDM cosmogony provided by N-body simulations. They incorporate the physical processes that affect the baryonic component, with the advantage of reaching a larger dynamic range than fully selfconsistent hydro-simulations at a far smaller computational cost.