The Canada-UK Deep Submillimeter Survey. IV. The Survey of the 14 Hour Field

We have used SCUBA to survey an area of ≃ 50 arcmin 2, detecting 19 sources down to a 3σ sensitivity limit of ∼3.5 mJy at 850µm. Monte-Carlo simulations have shown that the fluxes of sources in this and similar SCUBA surveys are biased upwards by the effects of source confusion and noise, leading to an overestimate by a factor of ∼1.4 in the fraction of the 850µm background that has been resolved by SCUBA. Once a correction is made for this effect, about 20 % of the background has been resolved. The simulations have also been used to quantify the effects of confusion on source positions. Of the 19 SCUBA sources, five are µJy radio sources and two are ISO 15µm sources. The radio/submillmetre flux ratios imply that the dust in these galaxies is being heated by young stars rather than AGN. The upper limit to the average 450µm/850µm flux ratio implies either that the SCUBA galaxies are at z 2 or, if they are at lower redshifts, that the dust is generally colder than in ULIRGs. We have used simple evolution models to address the major questions about the SCUBA sources: (1) what fraction of the star formation at high redshift is hidden by