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Hydrodynamical simulations of galaxy formation: effects of supernova feedback

We numerically simulate some of the most critical physical processes in galaxy formation: The supernova feedback, in conjunction with gasdynamics and gravity, plays a crucial role in determining how galaxies arise within the context of a model for large-scale structure. Our treatment incorporates a multi-phase model of the interstellar medium and includes the effects of cooling, heating and metal enrichment by supernovae, and evaporation of cold clouds. The star formation happens inside the clouds of cold gas, which are produced via thermal instability. We simulate the galaxy formation in standard biased CDM model for a variety of parameters and for several resolutions in the range 2--20$h^{-1}$kpc. In our picture, supernova feedback regulates the evolution of the gas components and star formation. The efficiency of cloud evaporation by supernova strongly influences star formation rates. This feedback results in a steady rate of star formation in large galaxies (mass larger than $2-3x10^{11}\Msun$) at a level of $(1-10)\Msun\yr$ for $z<3$. Supernova feedback has an even stronger effect on the evolution of dwarf galaxies, most of which have a small fraction of stars and extremely low luminosities: $M_R>-15$. In the case of both large and small galaxies, the distribution of luminous matter (stars) is strongly BIASED with respect to the dark matter. We find an approximate biasing measure of the form $ρ_{lum}= (ρ_{dm}/133)^{1.7}$ for z=0 and overdensities exceeding 1000. Deviations from this relation (a factor 2-3) depend on the environment. For halo masses exceeding $2x10^{10}\Msun$, the dependence of the absolute magnitude on the total mass can be approximated as $M_V=-18.5-4\log(M_{tot}/10^{11}\Msun)$, with a scatter of less than 0.5mag.