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X-ray study of a sample of FR0 radio galaxies: unveiling the nature of the central engine

X-ray study of a sample of FR0 radio galaxies: unveiling the nature of the central engine
X-ray study of a sample of FR0 radio galaxies: unveiling the nature of the central engine
Fanaroff–Riley type 0 radio galaxies (FR0s) are compact radio sources that represent the bulk of the radio-loud active galactic nuclei (AGN) population, but they are still poorly understood. Pilot studies on these sources have been already performed at radio and optical wavelengths: here we present the first X-ray study of a sample of 19 FR0 radio galaxies selected from the Sloan Digital Sky Survey/NRAO VLA Sky Survey/Faint Images of the Radio Sky at Twenty-cm sample of Best & Heckman, with redshift ≤0.15, radio size ≤10 kpc, and optically classified as low-excitation galaxies. The X-ray spectra are modelled with a power-law component absorbed by Galactic column density with, in some cases, a contribution from thermal extended gas. The X-ray photons are likely produced by the jet as attested by the observed correlation between X-ray (2–10 keV) and radio (5 GHz) luminosities, similar to Fanaroff–Riley type I radio galaxies (FRIs). The estimated Eddington-scaled luminosities indicate a low accretion rate. Overall, we find that the X-ray properties of FR0s are indistinguishable from those of FRIs, thus adding another similarity between AGN associated with compact and extended radio sources. A comparison between FR0s and low-luminosity BL Lacs rules out important beaming effects in the X-ray emission of the compact radio galaxies. FR0s have different X-ray properties with respect to young radio sources (e.g. gigahertz-peaked spectrum/compact steep spectrum sources), generally characterized by higher X-ray luminosities and more complex spectra. In conclusion, the paucity of extended radio emission in FR0s is probably related to the intrinsic properties of their jets that prevent the formation of extended structures, and/or to intermittent activity of their engines.
0035-8711
5535-5547
Torresi, E
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Grandi, P.
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Capetti, A.
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Baldi, Ranieri Diego
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giovannini, G
69c21e2b-1e77-441e-a103-1eddcc560e63
Torresi, E
8ca2ab9f-7689-4c9a-9a32-68b6554686bf
Grandi, P.
dc72fd8c-579e-45cc-b360-bc56397dbce9
Capetti, A.
1e4d3117-8900-47a5-8fe1-37b1b1574a5c
Baldi, Ranieri Diego
c416ed4c-5d1c-48ee-989c-3a8ab38cd124
giovannini, G
69c21e2b-1e77-441e-a103-1eddcc560e63

Torresi, E, Grandi, P., Capetti, A., Baldi, Ranieri Diego and giovannini, G (2018) X-ray study of a sample of FR0 radio galaxies: unveiling the nature of the central engine. Monthly Notices of the Royal Astronomical Society, 5535-5547. (doi:10.1093/mnras/sty520).

Record type: Article

Abstract

Fanaroff–Riley type 0 radio galaxies (FR0s) are compact radio sources that represent the bulk of the radio-loud active galactic nuclei (AGN) population, but they are still poorly understood. Pilot studies on these sources have been already performed at radio and optical wavelengths: here we present the first X-ray study of a sample of 19 FR0 radio galaxies selected from the Sloan Digital Sky Survey/NRAO VLA Sky Survey/Faint Images of the Radio Sky at Twenty-cm sample of Best & Heckman, with redshift ≤0.15, radio size ≤10 kpc, and optically classified as low-excitation galaxies. The X-ray spectra are modelled with a power-law component absorbed by Galactic column density with, in some cases, a contribution from thermal extended gas. The X-ray photons are likely produced by the jet as attested by the observed correlation between X-ray (2–10 keV) and radio (5 GHz) luminosities, similar to Fanaroff–Riley type I radio galaxies (FRIs). The estimated Eddington-scaled luminosities indicate a low accretion rate. Overall, we find that the X-ray properties of FR0s are indistinguishable from those of FRIs, thus adding another similarity between AGN associated with compact and extended radio sources. A comparison between FR0s and low-luminosity BL Lacs rules out important beaming effects in the X-ray emission of the compact radio galaxies. FR0s have different X-ray properties with respect to young radio sources (e.g. gigahertz-peaked spectrum/compact steep spectrum sources), generally characterized by higher X-ray luminosities and more complex spectra. In conclusion, the paucity of extended radio emission in FR0s is probably related to the intrinsic properties of their jets that prevent the formation of extended structures, and/or to intermittent activity of their engines.

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X-ray study of a sample of FR0 radio galaxies: unveiling - Accepted Manuscript
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Accepted/In Press date: 22 February 2018
e-pub ahead of print date: 3 March 2018
Published date: June 2018

Identifiers

Local EPrints ID: 422270
URI: http://eprints.soton.ac.uk/id/eprint/422270
ISSN: 0035-8711
PURE UUID: 84880842-7833-4e69-b6f5-e723e6a1c46a

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Date deposited: 20 Jul 2018 16:30
Last modified: 13 Mar 2019 18:16

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Contributors

Author: E Torresi
Author: P. Grandi
Author: A. Capetti
Author: G giovannini

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