The faint radio source population at 15.7 GHz – II. Multi-wavelength properties

Abstract

A complete, flux density limited sample of 96 faint (> 0:5 mJy) radio sources is selected
\nfrom the 10C survey at 15.7 GHz in the Lockman Hole. We have matched this sample to a
\nrange of multi-wavelength catalogues, including SERVS, SWIRE, UKIDSS and optical data;
\nmulti-wavelength counterparts are found for 80 of the 96 sources and spectroscopic redshifts
\nare available for 24 sources. Photometric reshifts are estimated for the sources with multiwavelength
\ndata available; the median redshift of the sample is 0.91 with an interquartile range
\nof 0.84. Radio-to-optical ratios show that at least 94 per cent of the sample are radio loud,
\nindicating that the 10C sample is dominated by radio galaxies. This is in contrast to samples
\nselected at lower frequencies, where radio-quiet AGN and starforming galaxies are present
\nin significant numbers at these flux density levels. All six radio-quiet sources have rising
\nradio spectra, suggesting that they are dominated by AGN emission. These results confirm
\nthe conclusions of Paper I that the faint, flat-spectrum sources which are found to dominate
\nthe 10C sample below 1 mJy are the cores of radio galaxies. The properties of the 10C
\nsample are compared to the SKADS Simulated Skies; a population of low-redshift starforming
\ngalaxies predicted by the simulation is not found in the observed sample.