The CFHT Legacy Survey: The Morphology-Density Relation of Galaxies out to Z~1

Abstract

We study the relationships between galaxy total luminosity (M_g), morphology, color and environment as a function of redshift. We use a magnitude-limited sample of 65,624 galaxies in the redshift range 0<z<1.3 taken from one of the Canada-France-Hawaii Telescope Legacy Survey Deep Fields. We parametrize galaxy morphology according to the Sersic index n. Our n>2 number fractions at z=0.1 agree well with those based on SDSS galaxies. We find that the n>2 galaxy number fraction is constant with redshift in the field. However, for overdense environments this fraction is larger and increases towards lower redshifts, higher densities and higher luminosities. Rest-frame color-magnitude diagrams show that the color distribution is bimodal out to our redshift limit of z~1 with a prominent red-sequence of galaxies at 0.2<z<0.4 and a large blue-peak dominance at 0.8<z<1. We use this bimodality to define a red galaxy fraction (rest-frame u-g>1). For all environments, this fraction increases towards lower redshifts and higher luminosities. The red fraction within cluster-like regions changes 60% faster with redshift as compared to the field for M_g<-19.5. Using, for the first time, observations across many cluster-field interfaces distributed over a single, large volume, we trace the large-scale morphology-density relation and the Butcher-Oemler effect over a period of almost 8 Gyr.