A SCUBA scan-map of the Hubble Deep Field:: measuring the bright end of the submillimetre source counts

Using the 850-mum SCUBA camera on the JCMT and a scanning technique different from other sub-mm surveys, we have obtained a 125 arcmin(2) map centred on the Hubble Deep Field. The 1sigma sensitivity to point sources is roughly 3 mJy and thus our map probes the brighter end of the sub-mm source counts. We find six sources with a flux greater than about 12 mJy (>4sigma) and, after a careful accounting of incompleteness and flux bias, estimate the integrated density of bright sources N(> 12 mJy) = 164(-58)(+77) deg(-2) (68 per cent confidence bounds).