Extended X-ray emission from non-thermal sources in the COSMOS field: a detailed study of a large radio galaxy at z = 1.168

Jelić, Vibor and Smolčić, Vernesa and Finoguenov, Alexis and Tanaka, Masayuki and Civano, Francesca and Schinnerer, Eva and Cappelluti, Nico and Koekemoer, Anton (2012) Extended X-ray emission from non-thermal sources in the COSMOS field: a detailed study of a large radio galaxy at z = 1.168. Monthly Notices of the Royal Astronomical Society, 423 (3). pp. 2753-2763. ISSN 0035-8711

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Abstract

X-ray selected galaxy group samples are usually generated by searching for extended X-ray sources that reflect the thermal radiation of the intragroup medium. On the other hand, large radio galaxies that regularly occupy galaxy groups also emit in the X-ray window, and their contribution to X-ray selected group samples is still not well understood. In order to investigate their relative importance, we have carried out a systematic search for non-thermal extended X-ray sources in the Cosmic Evolution Survey (COSMOS) field. Based on the morphological coincidence of X-ray and radio extensions, out of 60 radio galaxies, and ∼300 extended X-ray sources, we find only one candidate where the observed extended X-ray emission arises from non-thermal processes related to radio galaxies. We present a detailed analysis of this source, and its environment. Our results yield that external inverse Compton emission of the lobes is the dominant process that generates the observed X-ray emission of our extended X-ray candidate, with a minor contribution from the gas of the galaxy group hosting the radio galaxy. Finally, we show that finding only one potential candidate in the COSMOS field (in a redshift range 0 < z < 6 and with radio luminosity between 1025 and 1030 W Hz−1) is consistent with expected X-ray counts arising from synchrotron lobes. This implies that these sources are not a prominent source of contamination in samples of X-ray selected clusters/groups, but they could potentially dominate the z > 1 cluster counts at the bright end (SX > 7 × 10−15 erg s−1 cm2).

Item Type: Article
Keywords: radiation mechanisms: non-thermal, radiation mechanisms: thermal, surveys, galaxies: active, radio continuum: galaxies, X-rays: galaxies: clusters
Date: 2012
Subjects: NATURAL SCIENCES > Physics > Astronomy and Astrophysics
Additional Information: © 2012 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2012 April 10. Received 2012 April 10; in original form 2011 August 8. Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided.
Divisions: Faculty of Science > Department of Physics
Publisher: Oxford University Press
Depositing User: Vernesa Smolčić
Date Deposited: 19 Apr 2016 08:59
Last Modified: 14 Oct 2016 07:34
URI: http://digre.pmf.unizg.hr/id/eprint/4762

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