The Hubble Deep Field North SCUBA Super-map -: I.: Submillimetre maps, sources and number counts

We investigate the emission of submillimetre-wave radiation from galaxies in a 165 arcmin(2) region surrounding the Hubble Deep Field North. The data were obtained from dedicated observing runs from our group and others using the SCUBA camera on the James Clerk Maxwell Telescope (JCMT), and combined using techniques specifically developed for low signal-to-noise ratio source recovery. The resulting 'Super-map' is derived from approximately 60 shifts of JCMT time, taken in a variety of observing modes and chopping strategies, and combined here for the first time. At 850 mum we detect 19 sources at >4sigma, including five not previously reported. We also list an additional 15 sources between 3.5 and 4.0sigma (where two are expected by chance). The 450-mum map contains five sources at >4sigma. We present a new estimate of the 850- and 450-mum source counts. The number of submillimetre galaxies we detect account for approximately 40 per cent of the 850-mum submillimetre background, and we show that mild extrapolations can reproduce it entirely. A clustering analysis fails to detect any significant signal in this sample of SCUBA-detected objects. A companion paper describes the multiwavelength properties of the sources.