†Based on observations made with ESO telescopes at the La Silla Paranal Observatory under programme IDs 083.A0360 and 085.A0359.
The large area KX quasar catalogue – I. Analysis of the photometric redshift selection and the complete quasar catalogue
Article first published online: 25 JUL 2012
© 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS
Monthly Notices of the Royal Astronomical Society
Volume 424, Issue 4, pages 2876–2895, 21 August 2012
How to Cite
Maddox, N., Hewett, P. C., Péroux, C., Nestor, D. B. and Wisotzki, L. (2012), The large area KX quasar catalogue – I. Analysis of the photometric redshift selection and the complete quasar catalogue. Monthly Notices of the Royal Astronomical Society, 424: 2876–2895. doi: 10.1111/j.1365-2966.2012.21427.x
‡Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC).
- Issue published online: 8 AUG 2012
- Article first published online: 25 JUL 2012
- Manuscript Accepted: 30 MAY 2012
- Manuscript Received: 30 MAY 2012
- the SDSS and SDSS-II
- the Alfred P. Sloan Foundation
- the Participating Institutions
- the National Science Foundation
- the US Department of Energy
- the National Aeronautics and Space Administration
- the Japanese Monbukagakusho
- the Max Planck Society and the Higher Education Funding Council for England
- quasars: general;
- infrared: general
The results of a large area, ∼600 deg2, K-band flux-limited spectroscopic survey for luminous quasars are presented. The survey utilizes the UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS) in regions of sky within the Sloan Digital Sky Survey (SDSS) footprint. The K-band excess (KX) of all quasars with respect to Galactic stars is exploited in combination with a photometric redshift/classification scheme to identify quasar candidates for spectroscopic follow-up observations. The data contained within this investigation will be able to provide new constraints on the fraction of luminous quasars reddened by dust with E(B − V) ≤ 0.5 mag. The spectroscopic sample is defined using the K-band, 14.0 ≤ K ≤ 16.6, and SDSS i-band limits of i = 19.5, 19.7 and 22.0 over sky areas of 287, 150 and 196 deg2, respectively. The survey includes >3200 known quasars from the SDSS and more than 250 additional confirmed quasars from the KX selection. A well-defined subsample of quasars in the redshift interval 1.0 ≤ z ≤ 3.5 includes 1152 objects from the SDSS and 172 additional KX-selected quasars. The quasar selection is >95 per cent complete with respect to known SDSS quasars and >95 per cent efficient, largely independent of redshift and i-band magnitude. The properties of the new KX-selected quasars confirm the known redshift-dependent effectiveness of the SDSS quasar selection and provide a sample of luminous quasars experiencing intermediate levels of extinction by dust. The catalogue represents an important step towards the assembly of a well-defined sample of luminous quasars that may be used to investigate the properties of quasars experiencing intermediate levels of dust extinction within their host galaxies or due intervening absorption line systems.