Beyond Simple AGN Unification with Chandra-observed 3CRR Sources at 0.5 < z < 1

Joanna Kuraszkiewicz, Belinda J. Wilkes, Adam Atanas, Johannes Buchner, Jonathan C. McDowell, S. P. Willner, Matthew L.N. Ashby, Mojegan Azadi, Peter Barthel, Martin Haas, Diana M. Worrall, Mark Birkinshaw, Robert Antonucci, Rolf Chini, Giovanni G. Fazio, Charles Lawrence, Patrick Ogle

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Abstract

Low-frequency radio selection finds radio-bright galaxies regardless of the amount of obscuration by gas and dust. We report Chandra observations of a complete 178 MHz-selected, and so orientation-unbiased, sample of 44 0.5 < z < 1 3CRR sources. The sample is comprised of quasars and narrow-line radio galaxies (NLRGs) with similar radio luminosities, and the radio structure serves as both an age and an orientation indicator. Consistent with unification, intrinsic obscuration (measured by N H, X-ray hardness ratio, and X-ray luminosity) generally increases with inclination. However, the sample includes a population not seen in high-z 3CRR sources: NLRGs viewed at intermediate inclination angles with N H < 1022 cm-2. Multiwavelength analysis suggests that these objects have lower L/L Edd than typical NLRGs at similar orientation. Thus, both orientation and L/L Edd are important, and a "radiation-regulated unification"provides a better explanation of the sample's observed properties. In comparison with the 3CRR sample at 1 < z < 2, our lower-redshift sample shows a higher fraction of Compton-thin NLRGs (45% versus 29%) but a similar Compton-thick fraction (20%), implying a larger covering factor of Compton-thin material at intermediate viewing angles and thus a more "puffed-up"torus atmosphere. We posit that this is due to a range of L/L Edd extending to lower values in this sample. In contrast, at high redshifts, the narrower range and high L/L Edd values allowed orientation (and so simple unification) to dominate the sample's observed properties.

Original languageEnglish
Article number134
Number of pages29
JournalAstrophysical Journal
Volume913
Issue number2
DOIs
Publication statusPublished - 1-Jun-2021

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