The SCUBA 8-mJy survey -- I. Submillimetre maps, sources and number counts

We present maps, source lists and derived number counts from the largest, unbiased, extragalactic submillimetre (submm) survey so far undertaken with the SCUBA camera on the James Clerk Maxwell Telescope (JCMT). Our maps are located in two regions of sky (ELAIS N2 and Lockman-Hole E) and cover 260 arcmin 2 , to a typical rms noise level of s 850 . 2:5 mJy beam 21 . We have reduced the data using both the standard JCMT SURF procedures, and our own IDL-based pipeline which produces zero-footprint maps and noise images. The uncorrelated noise maps produced by the latter approach have enabled us to apply a maximum likelihood method to measure the statistical significance of each peak in our maps, leading to properly quantified errors on the flux density of all potential sources.