SUMSS: a wide-field radio imaging survey of the southern sky - II. The source catalogue

This paper is the second in a series describing the Sydney University Molonglo Sky Survey (SUMSS) being carried out at 843 MHz with the Molonglo Observatory Synthesis Telescope (MOST). The survey will consist of similar to590 4.3degreesx 4.3degrees mosaic images with 45 x 45 cosec\delta\ arcsec(2) resolution, and a source catalogue. In this paper we describe the initial release (version 1.0) of the source catalogue consisting of 107 765 radio sources made by fitting elliptical Gaussians in 271 SUMSS 4.3degreesx 4.3degrees mosaics to a limiting peak brightness of 6 mJy beam(-1) at delta less than or equal to -50degrees and 10 mJy beam(-1) at delta > -50degrees. The catalogue covers approximately 3500 deg(2) of the southern sky with delta less than or equal to -30degrees, about 43 per cent of the total survey area. Positions in the catalogue are accurate to within 1-2 arcsec for sources with peak brightness A (843) greater than or equal to 20 mJy beam(-1) and are always better than 10 arcsec. The internal flux density scale is accurate to within 3 per cent. Image artefacts have been classified using a decision tree, which correctly identifies and rejects spurious sources in over 96 per cent of cases. Analysis of the catalogue shows that it is highly uniform and is complete to 8 mJy at delta less than or equal to -50degrees and 18 mJy at delta > -50degrees. In this release of the catalogue about 7000 sources are found in the overlap region with the National Radio Astronomy Observatories Very Large Array Sky Survey at 1.4 GHz. We calculate a median spectral index of alpha = -0.83 between 1.4 GHz and 843 MHz. This version of the catalogue will be released via the World Wide Web with future updates as new mosaics are released.