Effects of Supernovae on the Early Evolution of Galaxies

Abstract

During the early evolution of an elliptical galaxy, some of the residual interstellar gas is heated to high temperatures by supernova explosions and is driven out of the galaxy in a galactic wind. The energy supplied per supernova is typically reduced about an order of magnitude by radiative cooling of supernova remnants, but the remaining energy is still sufficient to cause significant gas loss, particularly for small galaxies. In galaxies of smaller mass, gas loss begins earlier and carries away a larger fraction of the initial mass, owing to the lower escape velocity. Model collapse calculations show that the effect of early gas loss is to cause galaxies of smaller mass to have less condensed nuclei, smaller average metal abundances, and smaller metal abundance gradients, in qualitative agreement with the observations.