Evolution of the u-band luminosity function from redshift 1.2 to 0

Abstract

We produce and analyse u-band luminosity functions for the red and blue populations of galaxies using data from the Sloan Digital Sky Survey (SDSS) u-band Galaxy Survey (uGS) and Deep Evolutionary Exploratory Probe 2 (DEEP2) survey. From a spectroscopic sample of 41575 SDSS uGS galaxies and 24561 DEEP2 galaxies, we produce colour magnitude diagrams and make use of the colour bimodality of galaxies to separate red and blue populations. Luminosity functions for eight redshift slices in the range 0.01 < z < 1.2 are determined using the 1/Vmax method and fitted with Schechter functions showing that there is significant evolution in M-star, with a brightening of 1.4 mags for the combined population. The integration of the Schechter functions yields the evolution in the u-band luminosity density out to z ~ 1. By parametrizing the evolution as density proportional to (1+z)^beta, we find that beta = 1.36 +- 0.2 for the combined populations and beta = 2.09 +- 0.2 for the blue population. By removing the contribution of the old stellar population to the u-band luminosity density and correcting for dust attenuation, we estimate the evolution in the star formation rate of the Universe to be beta(SFR) = 2.5 +- 0.3. Discrepancies between our result and higher evolution rates measured using the infrared and far-UV can be reconciled by considering possibilities such as an underestimated dust correction at high redshifts or evolution in the stellar initial mass function.