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

We present the first results of a deep unbiased submillimetre survey carried out at 450 and 850μm. We detected 12 sources at 850 μm, giving a surface density of sources with S850μm > 2.8 mJy of 0.49± 0.16 arcmin . The sources constitute 20-30% of the background radiation at 850μm and thus a significant fraction of the entire 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 make these objects excellent candidates for being proto-ellipticals. 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 submillimetre survey of the local universe, we show that both the submillimetre source density and background can be explained if the submillimetre luminosity density evolves in a similar way to the UV -luminosity density. Thus, if these sources are ellipticals in the process of formation, they may be forming at relatively modest redshifts. Department of Physics and Astronomy, Cardiff University, P.O. Box 913, Cardiff CF2 3YB, UK Department of Astronomy, University of Toronto, 60 St. George Street, Toronto, Ontario M5S 1A1, Canada Mullard Space Science Laboratory, University of London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK CITA, University of Toronto, 60 St. George Street, Toronto, Ontario M5S 1A1, Canada DAEC, Observatoire de Paris-Meudon, 92195 Meudon, France Laboratoire d’Astronomie Spatiale, Traverse de Siphon, B.P.8 13376, Marseilles Cedex 12, France Dominion Astrophysical Observatory, 5071 W. Saanich Road, Victoria, BC, V8X 4M6, Canada