The CNOC2 Field Galaxy Luminosity Function I: A Description of Luminosity Function Evolution

We examine the evolution of the galaxy luminosity function (LF) using a sample of over 2000 galaxies, with 0.12 < z < 0.55 and 17.0 < Rc < 21.5, drawn from the Canadian Network for Observational Cosmology Field Galaxy Redshift Survey (CNOC2), at present the largest such sample at intermediate redshifts. We use UBVRcIc photometry and the spectral energy distributions (SED’s) of Coleman, Wu, & Weedman (1980) to classify our galaxies into early, intermediate, and late types, for which we compute luminosity functions in the rest-frame B, Rc, and U bandpasses. In particular, we adopt a convenient parameterization of LF evolution including luminosity and number density evolution, and take care to quantify correlations among our LF evolution parameters. We also carefully measure and account for sample selection effects as functions of galaxy magnitude and color. Our principal result is a clear quantitative separation of luminosity and density evolution for different galaxy populations, and the finding that the character of the LF evolution is strongly dependent on galaxy type. Specifically, we find that the earlyand intermediate-type LF’s show primarily brightening at higher redshifts and only modest Department of Astronomy, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8, Canada, lin, hyee, carlberg, sawicki, [email protected] Now at Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721, USA, [email protected] Hubble Fellow Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, Victoria, BC V8X 4M6, Canada, [email protected] Now at California Institute of Technology, 320-47, Pasadena, CA 91125, USA, [email protected] Department of Physics & Astronomy, University of Victoria, P.O. Box 3055, Victoria, BC V8W 3P6, Canada, [email protected] Now at W. M. Keck Observatory, Kamuela, HI 96743, USA, [email protected] Visiting Astronomer, Canada-France-Hawaii Telescope, which is operated by the National Research Council of Canada, the Centre Nationale de la Recherche Scientifique of France, and the University of Hawaii.