The evolution of radio sources in the UKIDSS-DXS–XMM-LSS field


  • Kim McAlpine,

    Corresponding author
    1. Department of Physics and Electronics, Rhodes University, Grahamstown 6139, South Africa
    Search for more papers by this author
  • Matt J. Jarvis

    1. Centre for Astrophysics, Science & Technology Research Institute, University of Hertfordshire, Hatfield, Herts AL10 9AB
    2. Physics Department, University of the Western Cape, Cape Town 7535, South Africa
    Search for more papers by this author



We investigate the cosmic evolution of low-luminosity (L1.4 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/Vmax 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 Kz 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.