The Optical and Near‐Infrared Properties of Galaxies. I. Luminosity and Stellar Mass Functions

Abstract

We use a large sample of galaxies from the Two Micron All Sky Survey (2MASS)\nand the Sloan Digital Sky Survey (SDSS) to calculate galaxy luminosity and\nstellar mass functions in the local Universe. We estimate k-corrections,\nevolution corrections, and stellar mass-to-light ratios (M/Ls) by fitting the\ngalaxy colors with simple models. Our optical and near-infrared luminosity\nfunctions agree with most recent literature optical and near-infrared\ndeterminations within the uncertainties. We argue that 2MASS is biased against\nlow surface brightness galaxies, and use SDSS plus our knowledge of stellar\npopulations to estimate that the true K-band luminosity function has a steeper\nfaint end slope than the direct estimate. Assuming a universally-applicable\nstellar initial mass function (IMF), we derive the stellar mass function of\ngalaxies. The faint end slope slope for the stellar mass function is steeper\nthan -1.1, reflecting the low stellar M/Ls characteristic of low-mass galaxies.\nWe estimate an upper limit to the stellar mass density in the local Universe\nOmega* h = 0.0020+/-0.0006 by assuming an IMF as rich in low-mass stars as\nallowed by observations of galaxy dynamics. Finally, we find that the\ncharacteristic luminosity or mass of early-type galaxies is larger than for\nlater types, and the faint end slope is steeper for later types than for\nearlier types. Accounting for typing uncertainties, we estimate that at least\nhalf, and perhaps as much as 3/4, of the stellar mass in the Universe is in\nearly-type galaxies. We present also SDSS/2MASS color-M/L correlations, an\nupdated discussion of near-infrared stellar M/L estimates, and the\nvolume-corrected distribution of g and K-band stellar M/Ls as a function of\nstellar mass. [Abridged]\n