THE LUMINOSITY FUNCTION OF GALAXIES IN THE LAS-CAMPANAS REDSHIFT SURVEY

We present the r-band luminosity function for a sample of 18,678 galax ies, with average redshift z = 0.1, from the Las Campanas Redshift Sur vey (LCRS). The luminosity function may be fitted by a Schechter funct ion with M = -20.29 +/- 0.02 + 5 log h, alpha = -0.70 +/- 0.05, and p hi = 0.019 +/- 0.001 h(3) Mpc(-3), for absolute magnitudes -23.0 less than or equal to M - 5 log h less than or equal to -17.5 and h = H-0/ (100 km s(-1) Mpc(-1)). Over the same absolute magnitude range, the me an galaxy density is 0.029 +/- 0.002 h(3) Mpc(-3) for a volume extendi ng to cz = 60,000 km s(-1). We compare our luminosity function to that from other redshift surveys; in particular, our luminosity function n ormalization is consistent with that of the Stromlo-APM survey and is therefore a factor of 2 below the normalization implied by the b(J) ap proximate to 20 bright galaxy counts. Our normalization thus indicates that much more evolution is needed to match the faint galaxy count da ta, compared to minimal evolution models that normalize at b(J) approx imate to 20. Also, we show that our faint-end slope alpha = -0.7, thou gh ''shallower'' than typical previous values alpha = -1, results prim arily from fitting the detailed shape of the LCRS luminosity function, rather than from any absence of intrinsically faint galaxies from our survey. Finally, we find that the faint end of the luminosity functio n is dominated by galaxies with emission lines. Using [O II] lambda 37 27 equivalent width W-lambda = 5 Angstrom as the dividing line, we fin d significant differences in the luminosity functions of emission and nonemission galaxies, particularly in their alpha values; emission gal axies have Schechter parameters M = -20.03 +/- 0.03 + 5 log h and alp ha = -0.9 +/- 0.1, while nonemission galaxies are described by M = -2 0.22 +/- 0.02 + 5 log h and alpha = -0.3 + 0.1. The average [O II] lam bda 23727 equivalent widths do not change significantly with redshift, consistent with a star formation rate that stays constant over the de pths sampled by the LCRS. This result holds for galaxies of different luminosities and over the respective redshift ranges that these galaxi es may be observed, in particular up to about z = 0.2 for galaxies bri ghter than M.