Obscuration and orientation effects in a medium redshift (0.5 < z < 1) 3CRR sample observed by Chandra

J. Kuraszkiewicz, B. Wilkes, A. Atanas, J. Buchner, J. McDowell, M. Azadi, P. Barthel, M. Haas, D. Worrall, M. Birkinshaw, R. Antonucci, G. Fazio, C. Lawrence, P. Ogle



We study the obscuration and orientation effects in a complete, low radio frequency (178 MHz) selected, and hence orientation unbiased sample of medium redshift (0.5 < z < 1) 3CRR sources observed by Chandra. The sample includes powerful, FRII radio sources including 13 quasars, 22 narrow-line radio galaxies (NLRGs) and a low-excitation radio galaxy (LERG), all with matched radio luminosities (log L(178MHz)~35.3-36.5 erg/s/Hz). The quasars are bright and soft in X-rays and have high radio-core fractions indicating low obscuration (log NH < 22) and face-on inclination. The NLRGs have 10-1000 times weaker X-ray luminosities, have a wide range of hardness ratios and lower radio-core fractions, implying a range of obscuration (log NH > 20.5) and higher inclination angles. These properties together with the observed trend of increasing intrinsic column density with decreasing radio core fraction are roughly consistent with orientation-dependent obscuration as in Unification models. However, this sample includes a new population, not seen in the high redshift (z > 1) 3CRR sample (Wilkes et al. 2013) - NLRGs with unusually low intrinsic column density (log NH < 22), which are viewed at inclination angles, skimming the edge of the accretion disk/torus. Analysis of their multiwavelength properties suggests a low L/LEdd ratio compared to the high-NH NLRGs viewed at similar inclination angles. Hence a simple Unification model (sufficient to explain the X-ray properties of the 3CRR sample at high redshift) needs to include a range of L/LEdd ratios at medium-z. About 1/4 of the sources in the medium and high redshift 3CRR samples are Compton-thick, showing high L([OIII])/L(2-8keV) and L(IR)/L(2-8keV) ratios.
Originele taal-2English
TijdschriftBulletin of the American Astronomical Society
Nummer van het tijdschrift1
StatusPublished - 1-jan.-2020

235TH Meeting of the American Astronomical Society
- Honolulu, HI , United States
Duur: 4-jan.-20208-jan.-2020


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