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We present numerical simulations of hierarchical galaxy formation, including gasdynamics, star formation, and supernova feedback. The simulations model the collapse of isolated constant-density perturbations, initially in solid-body rotation and in Hubble flow The perturbations are made of dark and baryonic matter in a 10:1 ratio. Small-scale power is added using the Zel'dovich approximation, assuming a power-law slope of -2.5. We are successful in making a three-component system that resembles a spiral galaxy: a thin disk made of stars and gas, a spheroidal component made of stars, and a dark matter halo. The disk has a flat rotation curve and an exponential surface density and surface brightness profile. Many stars form in the dissipated gas cores of dark matter clumps that form during the collapse. The remaining gas merges to form a disk, while the dark matter and stars merge to form a spheroidal distribution. Most of the supernova energy is radiated away and does not greatly affect the evolution of the galaxy. The star formation history is combined with population synthesis models to determine the absolute and apparent brightness of the simulated galaxy in many color bands. Simulated observations are also made. The system is brightest during a burst of star formation that occurs as the disk forms. It first reaches its peak I-magnitude of 22 at z = 2 and is fainter than B = 24.5 at z = 1.
Neal Katz (Mon,) studied this question.