The WiggleZ Dark Energy Survey: star formation in UV-luminous galaxies from their luminosity functions

Abstract

We present the ultraviolet (UV) luminosity function of galaxies from the GALEX Medium Imaging Survey with measured spectroscopic redshifts from the first data release of the WiggleZ Dark Energy Survey. Our sample consists of 39 996 NUV < 22.8 emission line galaxies in the redshift range 0.1 < z < 0.9. This sample selects galaxies with high star formation rates: at 0.6 < z < 0.9 the median star formation rate is at the upper 95th percentile of optically selected (r < 22.5) galaxies and the sample contains about 50 per cent of all NUV < 22.8, 0.6 < z < 0.9 starburst galaxies within the volume sampled. The most luminous galaxies in our sample (−21.0 > M_NUV > −22.5) evolve very rapidly with a number density declining as (1 + z)5±1 from redshift z = 0.9 to 0.6. These starburst galaxies (MNUV < −21 is approximately a star formation rate of 30 M_⊙ yr^−1) contribute about 1 per cent of cosmic star formation over the redshift range z = 0.6–0.9. The star formation rate density of these very luminous galaxies evolves rapidly, as (1 + z)^4±1. Such a rapid evolution implies that the majority of star formation in these large galaxies must have occurred before z = 0.9. We measure the UV luminosity function in Δz = 0.05 redshift intervals spanning 0.1 < z < 0.9, and provide analytic fits to the results. Our measurements of the luminosity function over this redshift range probe further into the bright end (1–2 mag further) than previous measurements, e.g. Arnouts et al., Budavári et al. and Treyer et al., due to our much larger sample size and sampled volume. At all redshifts z > 0.55 we find that the bright end of the luminosity function is not well described by a pure Schechter function due to an excess of very luminous (MNUV < −22) galaxies. These luminosity functions can be used to create a radial selection function for the WiggleZ survey or test models of galaxy formation and evolution. Here we test the AGN feedback model in Scannapieco, Silk & Bouwens, and find that this AGN feedback model requires AGN feedback efficiency to vary with one or more of the following: stellar mass, star formation rate and redshift.

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