The Parkes Half-Jansky Flat-Spectrum Sample

We present a new sample of Parkes half-jansky flat-spectrum radio sources, having made a particular effort to find any previously unidentified sources. The sample contains 323 sources selected according to a flux limit of 0.5Jy at 2.7GHz, a spectral index measured between 2.7 and 5.0GHz of alpha_2.7/5.0>-0.5, where S(nu)~nu ^alpha, Galactic latitude |b|>20 deg and -45 deg< declination (B1950) <+10 deg. The sample was selected from a region 3.90 steradians in area. We have obtained accurate radio positions for all the unresolved sources in this sample, and combined these with accurate optical positions from digitized photographic sky survey data to check all the optical identifications. We report new identifications based on R- and Kn-band imaging and new spectroscopic measurements of many of the sources. We present a catalogue of the 323 sources, of which 321 now have identified optical counterparts and 277 have measured spectral redshifts.