A single primary-beam area centered on α = 13h00m37s, δ = 30°34arcmin (1950.0) near the north galactic pole was mapped with the Very Large Array at 1.49 GHz. There are 145 sources within 22.5 arcmin of the map center having map peak flux densities sp ≥ 70 μJy, of which 49 were optically identified with objects brighter than BJ ≡ 22.5 on a Palomar Schmidt IIIa-J plate. The sky density of sources stronger than 84 μJy was determined by direct counts of individual sources within 17 arcmin of the map center. The authors used the confusion P(D) distribution in the central 13×13 arcmin2 of the map to estimate the density of sources between 10 and 84 μJy. The mean radio-source sky densities probed are about 103per deg2 above 87 μJy and 104per deg2 above 10.5 μJy, comparable with the surface densities of all galaxies brighter than J ≡ +21 and J ≡ +23.5, respectively. An evolutionary model which fits the 1.4-GHz counts of radio sources associated with spiral galaxies was used to predict the sky densities and median redshifts of far-infrared (λ = 60 μ) sources as faint as 1 mJy.
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Mitchell et al. (1985) studied this question.