Luminosity functions for galaxies and quasars in the Spitzer Wide-area Infrared Extragalactic Legacy Survey

Abstract

We construct rest-frame luminosity functions (LFs) at 3.6, 4.5, 5.8, 8 and 24 m over the redshift range 0 < z < 2 for galaxies and 0 < z < 4 for optical quasi-stellar objects (QSOs), using optical and infrared (IR) data from the Spitzer Wide-area Infrared Extragalactic (SWIRE) Survey. The 3.6-and 4.5-m galaxy LFs show evidence for moderate positive luminosity evolution up to z 1.5, consistent with the passive ageing of evolved stellar populations. Their comoving luminosity density was found to evolve passively, gradually increasing out to z 0.5-1 but flattening, or even declining, at higher redshift. Conversely, the 24-m galaxy LF, which is more sensitive to obscured star formation and/or active galactic nuclei (AGN) activity, undergoes strong positive evolution, with the derived IR energy density and star formation rate (SFR) density (1 + z) with = 4.5 +0.7 -0.6 and the majority of this evolution occurring since z 1. Optical QSOs, however, show positive luminosity evolution in all bands, out to the highest redshifts (3 < z < 4). Modelling as