Simulating the formation and evolution of galaxies: Multi-phase description of the interstellar medium, star formation, and energy feedback

We present a multi-phase representation of the ISM in NB-TSPH simulations of galaxy formation and evolution with particular attention to the case of early-type galaxies. Cold gas clouds are described by the so-called sticky particles algorithm. They can freely move throughout the hot ISM medium; stars form within these clouds and the mass exchange among the three baryonic phases (hot gas, cold clouds, stars) is governed by radiative and Compton cooling and energy feedback by supernova (SN) explosions, stellar winds, and UV radiation. We also consider thermal conduction, cloud-cloud collisions, and chemical enrichment. Our model agrees with and improves upon previous studies on the same subject. The results for the star formation rate are very promising and agree with recent observational data on early-type galaxies. These models lend further support to the revised monolithic scheme of galaxy formation, which has recently been also strengthened by high redshift data leading to the so-called downsizing and top-down scenarios.