The very bright SCUBA galaxy count: looking for SCUBA galaxies with the Mexican hat wavelet

We present the results of a search for bright high-redshift galaxies in two large Submillimetre Common-User Bolometer Array (SCUBA) scan-maps of Galactic regions. A Mexican hat wavelet technique was used to locate point sources in these maps, which suffer high foreground contamination as well as typical scan-map noise signatures. A catalogue of point-source objects was selected and observed again in the submillimetre continuum, and in HCO+(3 --> 2) at zero redshift to rule out Galactic sources. No extragalactic sources were found. Simulations show that the survey was sensitive to sources with fluxes greater than or similar to 50 mJy, depending on the local background. These simulations result in upper limits on the 850-mum counts of SCUBA galaxies of 53 per deg(2) at 50 mJy and 2.9 per deg(2) at 100 mJy.