EDP Sciences
Free Access
Volume 399, Number 2, February IV 2003
Page(s) 469 - 487
Section Galactic structure and dynamics
DOI https://doi.org/10.1051/0004-6361:20021803

A&A 399, 469-487 (2003)
DOI: 10.1051/0004-6361:20021803

The Parkes quarter-Jansky flat-spectrum sample

2. New optical spectra and redshift measurements
I. M. Hook1, P. A. Shaver2, C. A. Jackson3, J. V. Wall1 and K. I. Kellermann4

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.)

(Received 16 May 2002 / Accepted 29 November 2002 )

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 $0.25~{\rm Jy} < S_{\rm 2.7~GHz}< 0.5~{\rm Jy}$, 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 Ly $\alpha$ and CIV emission lines have larger equivalent width in radio-loud quasars than radio-quiet QSOs to greater than the 3 $\sigma$ 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- $\alpha$ line ( $D_{\rm A}$) measured from these spectra show the same trend with redshift as for optically selected QSOs.

Key words: quasars: general

Offprint request: I. M. Hook, imh@astro.ox.ac.uk

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© ESO 2003

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