1306.0850 (Belinda J. Wilkes et al.)

Revealing the heavily obscured AGN population of High Redshift 3CRR Sources with Chandra X-ray Observations    [PDF]

Belinda J. Wilkes, Joanna Kuraszkiewicz, Martin Haas, Peter Barthel, Christian Leipski, S. P. Willner, D. M. Worrall, Mark Birkinshaw, Robert Antonucci, M. L. N. Ashby, Rolf Chini, G. G. Fazio, Charles Lawrence, Patrick Ogle, Bernhard Schulz

Chandra observations of a complete, flux-limited sample of 38 high-redshift (10) indicating obscuration (log N_H ~ 22-24 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 high [OIII] 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 NGC1068). The ratios of unobscured to Compton-thin (10^{22}< N_H(int) < 1.5 x 10^{24} cm^-2) to CT (N_H(int) > 1.5 x 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 AGN 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 ~ 60deg and the obscuring material covers 30deg of which ~ 12deg is Compton thick. The multi-wavelength properties reveal that many NLRGs have intrinsic absorption 10-1000x higher than indicated by their X-ray hardness ratios, and their true L_X values are ~10--100x larger than the hardness-ratio absorption corrections would indicate.

View original: http://arxiv.org/abs/1306.0850