THE PARKES HALF-JANSKY FLAT-SPECTRUM SAMPLE

We present a new sample of Parkes half-jansky flat-spectrum radio sour ces, having made a particular effort to find any previously unidentifi ed sources. The sample contains 323 sources selected according to a fl ux limit of 0.5 Jy at 2.7 GHz, a spectral index measured between 2.7 a nd 5.0 GHz of alpha(2.7/5.0) > -0.5, where S(nu) proportional to nu(al pha), Galactic latitude \b\ > 20 degrees and -45 degrees < declination (B1950) < +10 degrees. The sample was selected from a region 3.90 ste radians in area. We have obtained accurate radio positions for all the unresolved sources in this sample, and combined these with accurate o ptical positions from digitized photographic sky survey data to check all the optical identifications. We report new identifications based o n 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 spectra l redshifts.