The dependence of the galaxy luminosity function on environment

We present luminosity functions for galaxies in loose groups in the Las Campanas Redshift Survey, differentiated by their environment (defined by the line-of-sight velocity dispersion sigma of the host groups) and also by their spectral type (emission or nonemission, defined by the equivalent width of the [O II] lambda 3727 line). We find systematic variations in the Schechter parameters alpha and M* for non-emission-line galaxies over a range of 0 < < 800 km s(-1): varies from 0.20 to -0.91, indicating an increase in the steepness of the faint end slope with increasing sigma. The accompanying variation in M* appears to be accounted for by the intrinsic correlation with a and does not indicate a significant physical variation in the bright end of the luminosity function. For emission-line galaxies, we find no significant systematic variation of the luminosity function with the environment. Our results show that emission and nonemission galaxies generally occupy two distinct regions in the alpha -M* parameter space. From our luminosity functions, we derive the number ratios of emission to nonemission galaxies as a function of environment and absolute magnitude, showing that the relative abundance of non-emission-line galaxies generally increases for all magnitudes -23 < M-R < -17.5 toward high-sigma environments, from similar to 80% to more than 90% at M-R = - 22 and from similar to 10% to more than 50% at M-R = -18 (H-0 = 100 km s(-1) Mpc(-1) and q(0) = 0.5).