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IGR J16351?5806: another close by Compton-thick AGN

IGR J16351?5806: another close by Compton-thick AGN
IGR J16351?5806: another close by Compton-thick AGN
IGR J16351?5806 has been associated with the Seyfert 2 galaxy ESO 137?G34, having been first reported as a high energy emitter in the third INTEGRAL / Imager on Board the INTEGRAL Satellite survey. Using a new diagnostic tool based on X-ray column density measurements versus softness ratios (F2-10 keV/F20-100 keV) , we have previously identified this source as a candidate Compton-thick active galactic nuclei (AGN). In the present work, we have analysed combined XMM–Newton and INTEGRAL data of IGR J16351?5806 in order to study its broad-band spectrum and investigate its Compton-thick nature. The prominent K? fluorescence line around 6.4 keV (EW > 1 keV) together with a flat 2–10 keV spectrum immediately point to a highly obscured source. The overall spectrum can be interpreted in terms of a transmission scenario where some of the high energy radiation is able to penetrate through the thick absorption and be observed together with its reflection from the surface of the torus. A good fit is also obtained using a pure reflection spectrum; in this case, the primary continuum is totally depressed and only its reflection is observed. An alternative possibility is that of a complex absorption, where two layers of absorbing matter each partially covering the central nucleus are present in IGR J16351?5806. All three scenarios are compatible from a statistical viewpoint and provide reasonable AGN spectral parameters; more importantly all point to a source with an absorbing column greater than 1.5 × 1024 cm?2 , that is to a Compton-thick AGN. Because of this heavy obscuration, some extra components which would otherwise be hidden are able to emerge at low energies and can be studied; a thermal component with kT in the range 0.6–0.7 keV and free metal abundance is statistically required in all three scenarios while a scattered power law is only present in the pure reflection model. By providing strong evidence for the Compton-thick nature of IGR J16351?5806, we indirectly confirm the validity of the Malizia et al. diagnostic diagram.
galaxies: active, galaxies: nuclei, galaxies: seyfert, x-rays: galaxies
0035-8711
L121-L125
Malizia, A.
efa63850-cf26-482c-ae3b-54b0c8fb8a87
Bassani, L.
07e5602c-f97e-4334-a0fa-c2212431a61a
Panessa, F.
ea57d0af-2ad5-4f65-a8f7-b001e70ebe13
De Rosa, A.
b2a68e71-5c23-4649-94f0-1d8ffd40bb77
Bird, A.J.
045ee141-4720-46fd-a412-5aa848a91b32
Malizia, A.
efa63850-cf26-482c-ae3b-54b0c8fb8a87
Bassani, L.
07e5602c-f97e-4334-a0fa-c2212431a61a
Panessa, F.
ea57d0af-2ad5-4f65-a8f7-b001e70ebe13
De Rosa, A.
b2a68e71-5c23-4649-94f0-1d8ffd40bb77
Bird, A.J.
045ee141-4720-46fd-a412-5aa848a91b32

Malizia, A., Bassani, L., Panessa, F., De Rosa, A. and Bird, A.J. (2009) IGR J16351?5806: another close by Compton-thick AGN. Monthly Notices of the Royal Astronomical Society, 394 (1), L121-L125. (doi:10.1111/j.1745-3933.2009.00622.x).

Record type: Article

Abstract

IGR J16351?5806 has been associated with the Seyfert 2 galaxy ESO 137?G34, having been first reported as a high energy emitter in the third INTEGRAL / Imager on Board the INTEGRAL Satellite survey. Using a new diagnostic tool based on X-ray column density measurements versus softness ratios (F2-10 keV/F20-100 keV) , we have previously identified this source as a candidate Compton-thick active galactic nuclei (AGN). In the present work, we have analysed combined XMM–Newton and INTEGRAL data of IGR J16351?5806 in order to study its broad-band spectrum and investigate its Compton-thick nature. The prominent K? fluorescence line around 6.4 keV (EW > 1 keV) together with a flat 2–10 keV spectrum immediately point to a highly obscured source. The overall spectrum can be interpreted in terms of a transmission scenario where some of the high energy radiation is able to penetrate through the thick absorption and be observed together with its reflection from the surface of the torus. A good fit is also obtained using a pure reflection spectrum; in this case, the primary continuum is totally depressed and only its reflection is observed. An alternative possibility is that of a complex absorption, where two layers of absorbing matter each partially covering the central nucleus are present in IGR J16351?5806. All three scenarios are compatible from a statistical viewpoint and provide reasonable AGN spectral parameters; more importantly all point to a source with an absorbing column greater than 1.5 × 1024 cm?2 , that is to a Compton-thick AGN. Because of this heavy obscuration, some extra components which would otherwise be hidden are able to emerge at low energies and can be studied; a thermal component with kT in the range 0.6–0.7 keV and free metal abundance is statistically required in all three scenarios while a scattered power law is only present in the pure reflection model. By providing strong evidence for the Compton-thick nature of IGR J16351?5806, we indirectly confirm the validity of the Malizia et al. diagnostic diagram.

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More information

Published date: March 2009
Keywords: galaxies: active, galaxies: nuclei, galaxies: seyfert, x-rays: galaxies

Identifiers

Local EPrints ID: 144785
URI: http://eprints.soton.ac.uk/id/eprint/144785
ISSN: 0035-8711
PURE UUID: c65da215-4db3-4bbe-ba8f-d0b9f34a1d6a
ORCID for A.J. Bird: ORCID iD orcid.org/0000-0002-6888-8937

Catalogue record

Date deposited: 24 May 2010 14:35
Last modified: 09 Nov 2021 02:44

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Contributors

Author: A. Malizia
Author: L. Bassani
Author: F. Panessa
Author: A. De Rosa
Author: A.J. Bird ORCID iD

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