The Parkes quarter-Jansky flat-spectrum sample^*

2. New optical spectra and redshift measurements

¹ Department of Physics, University of Oxford, Nuclear & Astrophysics Laboratory, Keble Road, Oxford, OX1 3RH, UK
² European Southern Observatory, Karl Schwarzschild Straße 2, 85748 Garching b. München, Germany
³ Research School of Astronomy & Astrophysics, The Australian National University, Mount Stromlo Observatory, Canberra, Australia
⁴ National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, USA (The National Radio Astronomy Observatory is operated by Associated Universities Inc. under a cooperative agreement with the National Science Foundation.)

Corresponding author: I. M. Hook, imh@astro.ox.ac.uk

Received: 16 May 2002
Accepted: 29 November 2002

Abstract

We present optical spectra and redshift measurements for 178 flat-spectrum objects from the Parkes quarter-Jansky flat-spectrum sample. These spectra were obtained in order to compile a complete sample of quasars for use in a study of quasar evolution. We present a composite optical spectrum made from the subset of 109 quasars that have flux densities in the range , and make a comparison with a composite for radio-quiet QSOs from the Large Bright Quasar Survey. Our large sample of radio-loud quasars allows us to strengthen previous reports that the Lyα and CIV emission lines have larger equivalent width in radio-loud quasars than radio-quiet QSOs to greater than the 3σ level. However we see no significant difference in the equivalent widths of CIII] or MgII. We also show that the flux decrements across the Lyman-α line (D_A) measured from these spectra show the same trend with redshift as for optically selected QSOs.