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

Abstract

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 ~ 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 (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.

42 pages, 11 figures, 3 tables; ApJ, in press

References in corpus (20)

• The Cosmic Evolution Survey (COSMOS) -- Overview
• The synthesis of the cosmic X-ray background in the Chandra and XMM-Newton era
• The All-wavelength Extended Groth Strip International Survey (AEGIS) Data Sets
• The X-ray Properties of the Most-Luminous Quasars from the Sloan Digital Sky Survey
• X-ray spectral properties of AGN in the Chandra Deep Field South
• Absorption Properties and Evolution of Active Galactic Nuclei
• On the X-ray, optical emission line and black hole mass properties of local Seyfert galaxies
• Chandra and Spitzer unveil heavily obscured quasars in the SWIRE/Chandra Survey
• The Evolution of Obscuration in AGN
• Spitzer Reveals Hidden Quasar Nuclei in Some Powerful FR II Radio Galaxies
• Chandra Multiwavelength Project X-ray Point Source Catalog
• Measuring the Fraction of Obscured Quasars by the Infrared Luminosity of Unobscured Quasars
• 9.7 um Silicate Features in AGNs: New Insights into Unification Models
• A large population of mid-infrared selected, obscured active galaxies in the Bootes field
• X-ray Properties of the GigaHertz-Peaked and Compact Steep Spectrum Sources
• Extended inverse-Compton emission from distant, powerful radio galaxies
• The distribution of absorption in AGN detected in the XMM-Newton observations of the CDFS
• Near- and mid-infrared photometry of high-redshift 3CR sources
• X-ray reflection in the nearby Seyfert 2 galaxy NGC 1068
• The X-ray emission of the most luminous 3CR radio sources

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