2011MNRAS.413.1054M

We investigate the cosmic evolution of low-luminosity (L_1.4 GHz_< 10²⁵ W.Hz^–1.sr^–1) radio sources in the XMM Large Scale Structure Survey (XMM-LSS) field. We match low-frequency-selected (610-MHz) radio sources in the XMM-LSS field with near-infrared K-band observations over the same field from the UKIRT Infrared Deep Sky Survey. We use both the mean V/V_max statistic and the radio luminosity function of these matched sources to quantify the evolution of the comoving space density of the low-luminosity radio sources in our sample. Our results indicate that the low-luminosity sources evolve differently from their high-luminosity counterparts out to a redshift of z∼ 0.8. The derived luminosity function is consistent with an increase in the comoving space density of low-luminosity sources by a factor of ∼1.5 at z= 0.8. We show that the use of the K-z diagram for the radio source population, although coarser than a full photometric redshift analysis, produces consistent results with previous studies using approximately >10 band photometry. This offers a promising method for conducting similar analyses over the whole sky with future near- and mid-infrared surveys.