Discovery of radio-loud quasars with redshifts above 4 from the PMN sample

I. M. Hook; R. G. McMahon; P. A. Shaver; I. A. G. Snellen

doi:10.1051/0004-6361:20020869

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Volume 391 / No 2 (August IV 2002)

A&A, 391 2 (2002) 509-517

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Issue		A&A Volume 391, Number 2, August IV 2002


Page(s)		509 - 517
Section		Cosmology (including clusters of galaxies)
DOI		https://doi.org/10.1051/0004-6361:20020869
Published online		02 August 2002

A&A 391, 509-517 (2002)

Discovery of radio-loud quasars with redshifts above 4 from the PMN sample ^*,^**

I. M. Hook¹, R. G. McMahon², P. A. Shaver³ and I. A. G. Snellen⁴

¹ Department of Physics, University of Oxford, Nuclear & Astrophysics Laboratory, Keble Road, Oxford OX1 3RH, UK e-mail: imh@astro.ox.ac.uk
² Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
³ European Southern Observatory, Karl Schwarzschild Straße 2, 85748 Garching b. München, Germany
⁴ Institute for Astronomy, Royal Observatory, Edinburgh, EH9 3HJ, UK

Corresponding author: I. M. Hook, ihook@gemini.edu

Received: 5 February 2002
Accepted: 11 June 2002

Abstract

We present results of a new, large survey for high-redshift radio-loud quasars, which targets quasars with $z>4$ . The survey is based on the PMN and NVSS radio surveys, optically identified using digitised UKST B, R and I plates. Six new $z>4$ flat-spectrum QSOs have been discovered, and one previously known $z>4$ QSO rediscovered, based on their red optical colours. The QSOs discovered in this survey are bright in both radio and optical bands; in particular PMN J1451-1512 ( $z=4.763$ , $\rm I=17.3$ , $R=19.1$ ) and PMN J0324-2918 ( $z=4.630$ , $R=18.7$ ) are very luminous. PMN J1451-1512 at is also now the most distant radio-selected quasar. In addition, 9 new quasars with $3.5<z<4.0$ were discovered during the survey. We present spectra and finding charts for the new quasars. We also derive a surface density of $\rm 1.0\pm 0.4\times 10^{-3} ~sq\ deg^{-1}$ for flat-spectrum $z>4$ QSOs with $S\ge 72$ mJy and $\it R < 21$ mag.

Key words: quasars: general

^*

The work presented here is based in part on data obtained with the ESO facilities on La Silla (EFOSC/3.6-m).

^**

Figures 7 and 8 are only available in the electronic form at http://www.edpsciences.org

© ESO, 2002

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Discovery of radio-loud quasars with redshifts above 4 from the PMN sample *,**

Discovery of radio-loud quasars with redshifts above 4 from the PMN sample ^*,^**