The Second APM UKST Colour Survey for z > 4 quasars

Abstract

We present the spectra, positions, and finding charts for 31 bright (R<19.3) colour-selected quasars covering the redshift range z=3.85–4.78, with four having redshifts z>4.5. The majority are in the southern sky (δ<−25°). The quasar candidates were selected for their red (BJ−R≳2.5) colours from UK or POSSII Schmidt Plates scanned at the Automated Plate Measuring (APM) facility in Cambridge. Low-resolution (≳10 Å) spectra were obtained to identify the quasars, primarily at the Las Campanas Observatory. The highest redshift quasar in our survey is at z≈4.8(R=18.7) and its spectrum shows a damped Lyα absorption system at z=4.46. This is currently the highest redshift damped Lyα absorber detected. Five of these quasars exhibit intrinsic broad absorption line features. Combined with the previously published results from the first part of the APM United Kingdom Schmidt Telescope (UKST) survey we have now surveyed a total of ∼8000 deg^2 of sky i.e. 40 per cent of the high galactic latitude (|b|>30°) sky, resulting in 59 optically selected quasars in the redshift range 3.85 to 4.78; 49 of which have z≥4.00.

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