In this paper we numerically simulate some of the most critical physical processes in galaxy formation: The supernova feedback loop, in conjunction with gas dynamic processes and gravitational condensations, plays a crucial role in determining how the observable properties of 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. In this paper we simulate the galaxy formation in standard biased Cold Dark Matter (CDM) model for a variety of parameters and for several resolutions. In our picture, supernova feedback regulates the evolution of the gas components and star formation. The efficiency of cold 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 − 3) × 10 11 M ⊙ within 100 kpc radius) at a level of (1 − 10)M ⊙ per year for z < 3 (H 0 = 50 Km s −1 Mpc −1 ). Supernova feedback has an even stronger effect on the evolution of "dwarf" galaxies. Most of the dwarf galaxies in our models have a small fraction of stars and extremely low luminosities: M R > −15 for parent dark-halo masses M tot < (2 − 3) × 10 10 M ⊙ within a 50 kpc radius. The observational properties (colors, luminosities) of galaxies identified in the simulations are computed using a stellar population synthesis model. In the case of both large and small galaxies, the distribution of luminous matter (stars) is strongly biased with respect to the dark matter. For a range of parameter values and resolutions we find an approximate biasing measure of the form ρ lum = (ρ dm /133) 1.7 , for overdensities exceeding about 1000. Deviations from this relation depend strongly on the environment. For halo masses exceeding 2 × 10 10 M ⊙ , the dependence of the absolute visual magnitude M V on the total mass can be approximated as M V = −18.5 − 4 log(M tot /10 11 M ⊙ ), with a scatter of less than 1/2 magnitude.

Using 3D hydrodynamical simulations of galaxy formation with supernova feedback and a multiphase medium, we derive theoretical relations analogous to the observed Tully-Fisher (TF) relations in various photometric bands. This paper examines the influence of self-regulation mechanisms including supernova feedback on galaxy luminosi-a useful laboratory for testing various hypotheses and gaining insight into the physics responsible for the scatter, slope, and amplitude of the TF relation.

We have simulated the formation of large-scale structure arising from COBEnormalized spectra computed by convolving a primordial double-inflation perturbation spectrum with the CDM transfer function. Due to the broken scale invariance ('BSI') characterizing the primordial perturbation spectrum, this model has less small-scale power than the (COBE-normalized) standard CDM model. The particle-mesh code (with 512 3 cells and 256 3 particles) includes a model for thermodynamic evolution of baryons in addition to the usual gravitational dynamics of dark matter. It provides an estimate of the local gas temperature. In particular, our galaxy-finding procedure seeks peaks in the distribution of gas that has cooled. It exploits the fact that "cold" particles trace visible matter better than average and thus provides a natural biasing mechanism. The basic picture of large-scale structure formation in the BSI model is the familiar hierarchical clustering scenario. We obtain particle in cell statistics, the galaxy correlation function, the cluster abundance and the cluster-cluster correlation function and statistics for large and small scale velocity fields. We also report here on a semi-quantitative study of the distribution of gas in different temperature ranges. Based on confrontation with observations and comparison with standard CDM, we conclude that the BSI scenario could represent a promising modification of the CDM picture capable of describing many details of large-scale structure formation.

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