A deep radio and optical survey near the North Galactic Pole – IV. VLA observations and optical identifications of 5C 12 sources

VLA observations of 274 5C12 radio sources (S0.4>10 mJy) are reported. Together with radio data from other surveys, these provide positions for the sources which are accurate enough to permit identifications with optical images down to υ∼23 mag. To this level, one-third of a sample of 291 5C 12 sources are identified, mainly with stellar images and red extended images. The b–υ and υ–r colours of the majority of the stellar identifications fall within 0.4 mag of b–υ = 0.3, υ–r = 0.5, typical of QSO colours. Two of the stellar identifications are optically variable. One-third of the stellar identifications have flat (α>–0.5) radio spectra. The colours (b–υ, υ–r), magnitudes and light profiles of the red extended images are consistent with their being giant elliptical galaxies at redshifts 0.15