The Parkes quarter-Jansky flat-spectrum sample - I. Sample selection and source identifications

We present a new sample of quarter-Jansky at-spectrum radio sources selected to search for high-redshift quasars and to study the evolution of the at-spectrum quasar population. The sample comprises 878 radio sources selected from the Parkes catalogues with spectral indices alpha(2.7 GHz)(5 GHz) greater than or equal to -0.4 where Snu proportional to nu(alpha). The sample covers all right ascensions and the declination range from -80.degrees0 to +2.degrees5, excluding low galactic latitudes (\b\ < 10 degrees) and the Magellanic Cloud regions. We have obtained improved radio source positions, firstly to reconfirm the majority of the existing identifications, and secondly, using digitized sky-survey data and deep B, Gunn-i and Gunn-z CCD-imaging, to find optical identifications for 223 previously-unidentified sources. We present the final catalogue of 878 at-spectrum sources: 827 are compact radio sources identified with galaxies, quasars and BL Lac objects, 38 have either extended radio structure or are identified with Galactic objects (PN, HII or non-compact radio source), 4 are obscured by Galactic stars, and 9 (1 per cent of the total sample) remain unidentified.