EVOLUTION OF THE BLUE AND FAR-INFRARED GALAXY LUMINOSITY FUNCTIONS

We construct a blue band luminosity function from published spectroscopic surveys of faint field galaxies (b(j)> 20) and compare it to three recent determinations of the blue-selected field galaxy luminosity function in the local universe. We find evidence for density evolution for moderate luminosity galaxies ( - 17.5 > M(b) > - 21.5; h = 0. 5) at a rate of (1 + z)delta, with a best fit of delta = 4 +/- 2, between the current epoch and z greater than or similar to 0. 1. At M(b) < - 22 we find evidence for about 0.5-1.5 mag of luminosity evolution in addition to the density evolution, corresponding to an evolutionary rate of L approximately (1+z)gamma, gamma = 0.5-2.5, by a redshift of about 0.4, when the data are compared to the local luminosity function of de Lapparent et al [ApJ, 343, 1 (1989)]. However, in the presence of the above mentioned density evolution, no additional luminosity evolution is required to fit the M(b) < - 22 data if the local luminosity functions of either Efstathiou et al. [MNRAS, 232, 431, (1988)] or Loveday et al. [ApJ, 390, 338 (1992)] are used instead. Assuming a steeper faint end slope of alpha = -1.3, similar to that observed in the Virgo cluster, could explain the data with a luminosity evolution rate gamma = 1-2, without need for any density evolution. We compare the best-fitting composite density and luminosity evolution models to faint IRAS 60 mum source counts. The fits are quite acceptable, implying that the blue and far-infrared evolutionary rates may be similar.