The Canada‐UK Deep Submillimeter Survey: First Submillimeter Images, the Source Counts, and Resolution of the Background

Abstract

We present the first results of a deep unbiased submillimeter survey carried out at 450 and 850 μm. We detected 12 sources at 850 μm at greater than the 3 σ level, giving a surface density of sources with S 850μm >2.8 mJy of 0.49 ± 0.16 arcmin -2 . If replicated over the sky, our sources would generate a background at 850 μm of 9.6 × 10 −11 W m -2 sr -1 , which is ≃20% of the value measured by the Far-Infrared Absolute Spectrophotometer (FIRAS) and a significant fraction of the total background radiation produced by stars. This implies, through the connection between metallicity and background radiation, that a significant fraction of all the stars that have ever been formed were formed in objects like those detected here. The combination of their large contribution to the background radiation and their extreme bolometric luminosities makes these objects excellent candidates for being proto-elliptical galaxies. Optical astronomers have recently shown that the UV luminosity density of the universe increases by a factor of ≃10 between z =0 and z =1-2 and then decreases again at higher redshifts. Using the results of a parallel submillimeter survey of the local universe, we show that both the submillimeter source density and background radiation (as detected by FIRAS) can be explained if the submillimeter luminosity density evolves in a similar way to the UV luminosity density. Thus, if these sources are elliptical galaxies in the process of formation, they are probably forming at relatively modest redshifts.