An AzTEC 1.1 mm survey of the GOODS-N field - II. Multiwavelength identifications and redshift distribution

Abstract

We present results from a multi-wavelength study of 29 sources (false detection probabilities <5%) from a survey of the Great Observatories Origins Deep Survey-North field at 1.1mm using the AzTEC camera. Comparing with existing 850um SCUBA studies in the field, we examine differences in the source populations selected at the two wavelengths. The AzTEC observations uniformly cover the entire survey field to a 1-sigma depth of ~1mJy. Searching deep 1.4GHz VLA, and Spitzer 3--24um catalogues, we identify robust counterparts for 21 1.1mm sources, and tentative associations for the remaining objects. The redshift distribution of AzTEC sources is inferred from available spectroscopic and photometric redshifts. We find a median redshift of z=2.7, somewhat higher than z=2.0 for 850um-selected sources in the same field, and our lowest redshift identification lies at a spectroscopic redshift z=1.1460. We measure the 850um to 1.1mm colour of our sources and do not find evidence for `850um dropouts', which can be explained by the low-SNR of the observations. We also combine these observed colours with spectroscopic redshifts to derive the range of dust temperatures T, and dust emissivity indices $\beta$ for the sample, concluding that existing estimates T~30K and $\beta$~1.75 are consistent with these new data.