VLA 1.4GHz observations of the GOODS-North Field: Data Reduction and Analysis

摘要

We describe deep, new, wide-field radio continuum observations of the GreatObservatories Origins Deep Survey -- North (GOODS-N) field. The resulting maphas a synthesized beamsize of ~1.7" and an r.m.s. noise level of ~3.9uJy/bmnear its center and ~8uJy/bm at 15', from phase center. We have cataloged 1,230discrete radio emitters, within a 40' x 40' region, above a 5-sigma detectionthreshold of ~20uJy at the field center. New techniques, pioneered by Owen &Morrison (2008), have enabled us to achieve a dynamic range of 6800:1 in afield that has significantly strong confusing sources. We compare the 1.4-GHz(20-cm) source counts with those from other published radio surveys. Ourdifferential counts are nearly Euclidean below 100uJy with a median sourcediameter of ~1.2". This adds to the evidence presented by Owen & Morrison(2008) that the natural confusion limit may lie near ~1uJy. If the Euclideanslope of the counts continues down to the natural confusion limit as anextrapolation of our log N - log S, this indicates that the cutoff must befairly sharp below 1uJy else the cosmic microwave background temperature wouldincrease above 2.7K at 1.4 GHz.