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 ≳ 50 mJy, depending on the local background. These simulations result in upper limits on the 850-μm counts of SCUBA galaxies of 53 per deg2 at 50 mJy and 2.9 per deg2 at 100 mJy.