The Luminosity Function of Galaxies in SDSS Commissioning Data

Abstract

During commissioning observations, the Sloan Digital Sky Survey (SDSS) has\nproduced one of the largest existing galaxy redshift samples selected from CCD\nimages. Using 11,275 galaxies complete to r^* = 17.6 over 140 square degrees,\nwe compute the luminosity function of galaxies in the r^* band over a range -23\n< M < -16 (for h=1). The result is well-described by a Schechter function with\nparameters phi_* = 0.0146 +/- 0.0012 h^3 Mpc^{-3}, M_* = -20.83 +/- 0.03, and\nalpha = -1.20 +/- 0.03. The implied luminosity density in r^* is j = (2.6 +/-\n0.3) x 10^8 h L_sun Mpc^{-3}. The surface brightness selection threshold has a\nnegligible impact for M < -18. We measure the luminosity function in the u^*,\ng^*, i^*, and z^* bands as well; the slope at low luminosities ranges from\nalpha=-1.35 to alpha=-1.2. We measure the bivariate distribution of r^*\nluminosity with half-light surface brightness, intrinsic color, and morphology.\nHigh surface brightness, red, highly concentrated galaxies are on average more\nluminous than low surface brightness, blue, less concentrated galaxies. If we\nsynthesize results for R-band or b_j-band using the Petrosian magnitudes with\nwhich the SDSS measures galaxy fluxes, we obtain luminosity densities 2.0 times\nthat found by the Las Campanas Redshift Survey in R and 1.4 times that found by\nthe Two-degree Field Galaxy Redshift Survey in b_j. We are able to reproduce\nthe luminosity functions obtained by these surveys if we also mimic their\nisophotal limits for defining galaxy magnitudes, which are shallower and more\nredshift dependent than the Petrosian magnitudes used by the SDSS. (Abridged)\n