The Canada-UK deep submillimeter survey: First submillimeter images, the source counts, and resolution of the background

We present the first results of a deep unbiased submillimeter survey carrie d out at 450 and 850 mu m. We detected 12 sources at 850 mu m at greater th an the 3 a level, giving a surface density of sources with S-850 mu m > 2.8 mJy of 0.49 +/- 0.16 arcmin(-2). If replicated over the sky, our sources w ould generate a background at 850 mu m of 9.6 x 10(-11) W m(-2) sr(-1), whi ch is similar or equal to 20% of the value measured by the Far-Infrared Abs olute Spectrophotometer (FIRAS) and a significant fraction of the total bac kground radiation produced by stars. This implies, through the connection b etween 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 backgrou nd radiation and their extreme bolometric luminosities makes these objects excellent candidates for being proto-elliptical galaxies. Optical astronome rs have recently shown that the UV luminosity density of the universe incre ases by a factor of similar or equal to 10 between z = 0 and z = 1-2 and th en decreases again at higher redshifts. Using the results of a parallel sub millimeter survey of the local universe, we show that both the submillimete r source density and background radiation (as detected by FIRAS) can be exp lained if the submillimeter luminosity density evolves in a similar way to the UV luminosity density. Thus, if these sources are elliptical galaxies i n the process of formation, they are probably forming at relatively modest redshifts.