The Effects of Starbursts and Low-Surface-Brightness Galaxies on Faint Galaxy Models

Abstract

We present models predicting the magnitude, redshift, and color distributions of field galaxies. We explore whether a fading starburst scenario can account for the observations of faint blue galaxies. We marginally rule out a starburst scenario with a local IMF because the models predict too many nearby faint galaxies that are not observed. A burst model with a truncated IMF reproduces the counts and redshift distributions well but produces too blue a population. We show that surface brightness selection has a significant effect on the distributions. In particular, adding a population of low-surface brightness galaxies, known to exist locally, can explain the counts for $B_J<23$. They do not, however, account for the steepness of the counts at fainter magnitudes. Finally we show that the colors of galaxies in a $K$-band selected sample are too blue to be consistent with a constant star-formation rate, passive-evolution model.