A survey for high-redshift radio-loud quasars: optical spectroscopy of S<~0.2 Jy, flat-spectrum radio sources

We present optical spectroscopic data for a complete sample of 161 S_5GHz>=0.2 Jy, flat-spectrum radio sources. The sources were observed as part of a survey for high-redshift, radio-loud quasars, and were selected for spectroscopic follow-up based on criteria of red optical colour and unresolved optical counterpart, as measured from APM scans of POSS-I plates. 13 objects from the spectroscopic sample were found to be radio-loud quasars with z<~3, of which two were previously known. We give positions, E(red) magnitudes, O-E colours, 5-GHz radio fluxes, radio spectral indices, optical spectra and redshifts where possible for the spectroscopic sample. We also give finding charts for the z<~3 QSOs. The highest redshift object found is a QSO with z=4.30 (GB1508+5714, the subject of an earlier Letter). The sample also contains a z=3.05 QSO, GB1759+7539, which is optically very luminous (E=16.1). In addition, spectra are given for 18 S_5GHz>=0.2 Jy, flat-spectrum radio sources that do not form part of the complete sample.