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Title: Evidence for a large fraction of compton-thick quasars at high redshift
Authors: Martínez-Sansigre, A.
Rawlings, S.
Bonfield, D. G.
Martínez-Sansigre, A.
Mateos, S.
Watson, M.
Simpson, C.
Almaini, O.
Foucaud, S.
Sekiguchi, K.
Ueda, Y.
First Published: 1-Jul-2007
Publisher: Royal Astronomical Society (RAS)
Citation: Monthly Notices of the Royal Astronomical Society: LETTERS, 2007, 379 (1)
Abstract: Using mid-infrared and radio selection criteria, we pre-select a sample of candidate high-redshift type 2 quasars in the Subaru XMM–Newton Deep Field (SXDF). To filter out starburst contaminants, we use a Bayesian method to fit the spectral energy distributions (SEDs) between 24-μm and the B-band, obtain photometric redshifts, and identify the best candidates for high-z type 2 quasars. This leaves us with 12 zphot≥ 1.7 type 2 quasar candidates in an area ∼0.8 deg2, of which only two have secure X-ray detections. The two detected sources have estimated column densities NH∼ 2 & 3 × 1027 m−2, i.e. heavily obscured but Compton-thin quasars. Given the large bolometric luminosities and redshifts of the undetected objects, the lack of X-ray detections suggests extreme absorbing columns NH≳ 1028 m−2 are typical. We have found evidence for a population of ‘Compton-thick’ high-redshift type 2 quasars, at least comparable to, and probably larger than, the type 1 quasar population, although spectroscopic confirmation of their active galactic nuclei nature is important.
DOI Link: 10.1111/j.1745-3933.2007.00323.x
ISSN: 1745-3933
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2007 the authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Deposited with reference to the publisher’s archiving policy available on the SHERPA/RoMEO website.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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