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Revealing the Heavily Obscured Active Galactic Nucleus Population of High-redshift 3CRR Sources with Chandra X-Ray Observations

Wilkes, Belinda J. and Kuraszkiewicz, Joanna and Haas, Martin and Barthel, Peter and Leipski, Christian and Willner, S. P. and Worrall, D. M. and Birkinshaw, Mark and Antonucci, Robert and Ashby, M. L. N. and Chini, Rolf and Fazio, G. G. and Lawrence, Charles and Ogle, Patrick and Schulz, Bernhard (2013) Revealing the Heavily Obscured Active Galactic Nucleus Population of High-redshift 3CRR Sources with Chandra X-Ray Observations. Astrophysical Journal, 773 (1). Art. No. 15. ISSN 0004-637X. doi:10.1088/0004-637X/773/1/15.

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Chandra observations of a complete, flux-limited sample of 38 high-redshift (1 < z < 2), low-frequency-selected (and so unbiased in orientation) 3CRR radio sources are reported. The sample includes 21 quasars (=broad-line radio galaxies) and 17 narrow-line radio galaxies (NLRGs) with matched 178 MHz radio luminosity (log L_R(5 GHz) ~44-45). The quasars have high radio core fraction, high X-ray luminosities (log L_X ~45-46), and soft X-ray hardness ratios (HR ~–0.5) indicating low obscuration. The NLRGs have lower core fraction, lower apparent X-ray luminosities (log L_X ~43-45), and mostly hard X-ray hardness ratios (HR >0) indicating obscuration (N_H ~10^(22)-10^(24) cm^(–2)). These properties and the correlation between obscuration and radio core fraction are consistent with orientation-dependent obscuration as in unification models. About half the NLRGs have soft X-ray hardness ratios and/or a high [O III] emission line to X-ray luminosity ratio suggesting obscuration by Compton thick (CT) material so that scattered nuclear or extended X-ray emission dominates (as in NGC 1068). The ratios of unobscured to Compton-thin (10^(22) cm^(–2) < N_H(int) <1.5 × 10^(24) cm^(–2)) to CT (N_H(int) >1.5 × 10^(24) cm^(–2)) is 2.5:1.4:1 in this high-luminosity, radio-selected sample. The obscured fraction is 0.5, higher than is typically reported for active galactic nuclei at comparable luminosities from multi-wavelength surveys (0.1-0.3). Assuming random nuclear orientation, the unobscured half-opening angle of the disk/wind/torus structure is ~60° and the obscuring material covers 30°, ~12° of which is CT. The multi-wavelength properties reveal that many NLRGs have intrinsic absorption 10-1000 × higher than indicated by their X-ray hardness ratios, and their true L_X values are ~10-100× larger than the hardness-ratio absorption corrections would indicate.

Item Type:Article
Related URLs:
URLURL TypeDescription DOIArticle
Wilkes, Belinda J.0000-0003-1809-2364
Willner, S. P.0000-0002-9895-5758
Ashby, M. L. N.0000-0002-3993-0745
Fazio, G. G.0000-0002-0670-0708
Ogle, Patrick0000-0002-3471-981X
Additional Information:© 2013 The American Astronomical Society. Received 2013 February 26; accepted 2013 May 30; published 2013 July 19. Support for this work was provided by the National Aeronautics and Space Administration through Chandra Award Number G08-9106X, by the Chandra X-Ray Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics Space Administration under contract NAS8-03060 (Chandra X-Ray Center) and by the Smithsonian Institution Endowment, Scholarly Studies Program, fund 40488100HH0017. The scientific results in this article are based to a significant degree on observations made by the Chandra X-Ray Observatory (CXO). We thank Mark Avara and Margaret Yellen for their early work on this project.
Funding AgencyGrant Number
Chandra X-Ray CenterUNSPECIFIED
Smithsonian Institution40488100HH0017
Subject Keywords:quasars: general; X-rays: galaxies
Issue or Number:1
Record Number:CaltechAUTHORS:20130904-130436889
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Official Citation:Revealing the Heavily Obscured Active Galactic Nucleus Population of High-redshift 3CRR Sources with Chandra X-Ray Observations Belinda J. Wilkes et al. 2013 ApJ 773 15
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:41085
Deposited By: Tony Diaz
Deposited On:18 Sep 2013 17:21
Last Modified:10 Nov 2021 04:25

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