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A Compton-thick AGN in the barred spiral galaxy NGC 4785

A Compton-thick AGN in the barred spiral galaxy NGC 4785
A Compton-thick AGN in the barred spiral galaxy NGC 4785
We present X-ray observations of the active galactic nucleus (AGN) in NGC 4785. The source is a local Seyfert 2 which has not been studied so far in much detail. It was recently detected with high significance in the 15–60?keV band in the 66-month Swift/BAT (Burst Array Telescope) all sky survey, but there have been no prior pointed X-ray observations of this object. With Suzaku, we clearly detect the source below 10?keV, and find it to have a flat continuum and prominent neutral iron fluorescence line with equivalent width ?1?keV. Fitting the broad-band spectra with physical reflection models shows the source to be a Compton-thick AGN with NH of at least 2 × 1024?cm?2 and absorption-corrected 2–10?keV X-ray power L2?10 ? few times 1042 erg s?1. Realistic uncertainties on L2?10 computed from the joint confidence interval on the intrinsic power-law continuum photon index and normalization are at least a factor of 10. The local bona fide Compton-thick AGN population is highly heterogeneous in terms of WISE mid-infrared source colours, and the nucleus of NGC 4785 appears especially sub-dominant in the mid-infrared when comparing to other Compton-thick AGN. Such sources would not be easily found using mid-infrared selection alone. The extent of host galaxy extinction to the nucleus is not clear, though NGC 4785 shows a complex core with a double bar and inner disc, adding to the list of known Compton-thick AGN in barred host galaxies.
0035-8711
1845-1855
Gandhi, P.
5bc3b5af-42b0-4dd8-8f1f-f74048d4d4a9
Yamada, S.
24a35a4b-7a81-4ecb-ab8e-7f101db1d8e1
Ricci, C.
82c8f75d-8215-4054-8b69-4cd30ab2d774
Asmus, D.
ade84ff0-4867-4f85-b317-6db72e71ccc1
Mushotzky, R.F.
ef7a457a-cae6-46ec-ac83-6a8375fd05c4
Ueda, Y.
03f584c1-9f26-484f-91a3-cf69654b933e
Terashima, Y.
43faf876-c664-4460-a111-ddfb73d7761a
La Parola, V.
886e17a6-fb4e-4be1-ae9e-694ef28b2b6c
Gandhi, P.
5bc3b5af-42b0-4dd8-8f1f-f74048d4d4a9
Yamada, S.
24a35a4b-7a81-4ecb-ab8e-7f101db1d8e1
Ricci, C.
82c8f75d-8215-4054-8b69-4cd30ab2d774
Asmus, D.
ade84ff0-4867-4f85-b317-6db72e71ccc1
Mushotzky, R.F.
ef7a457a-cae6-46ec-ac83-6a8375fd05c4
Ueda, Y.
03f584c1-9f26-484f-91a3-cf69654b933e
Terashima, Y.
43faf876-c664-4460-a111-ddfb73d7761a
La Parola, V.
886e17a6-fb4e-4be1-ae9e-694ef28b2b6c

Gandhi, P., Yamada, S., Ricci, C., Asmus, D., Mushotzky, R.F., Ueda, Y., Terashima, Y. and La Parola, V. (2015) A Compton-thick AGN in the barred spiral galaxy NGC 4785. Monthly Notices of the Royal Astronomical Society, 449 (2), 1845-1855. (doi:10.1093/mnras/stv344).

Record type: Article

Abstract

We present X-ray observations of the active galactic nucleus (AGN) in NGC 4785. The source is a local Seyfert 2 which has not been studied so far in much detail. It was recently detected with high significance in the 15–60?keV band in the 66-month Swift/BAT (Burst Array Telescope) all sky survey, but there have been no prior pointed X-ray observations of this object. With Suzaku, we clearly detect the source below 10?keV, and find it to have a flat continuum and prominent neutral iron fluorescence line with equivalent width ?1?keV. Fitting the broad-band spectra with physical reflection models shows the source to be a Compton-thick AGN with NH of at least 2 × 1024?cm?2 and absorption-corrected 2–10?keV X-ray power L2?10 ? few times 1042 erg s?1. Realistic uncertainties on L2?10 computed from the joint confidence interval on the intrinsic power-law continuum photon index and normalization are at least a factor of 10. The local bona fide Compton-thick AGN population is highly heterogeneous in terms of WISE mid-infrared source colours, and the nucleus of NGC 4785 appears especially sub-dominant in the mid-infrared when comparing to other Compton-thick AGN. Such sources would not be easily found using mid-infrared selection alone. The extent of host galaxy extinction to the nucleus is not clear, though NGC 4785 shows a complex core with a double bar and inner disc, adding to the list of known Compton-thick AGN in barred host galaxies.

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More information

Accepted/In Press date: 16 February 2015
e-pub ahead of print date: 26 March 2015
Published date: May 2015
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 400053
URI: http://eprints.soton.ac.uk/id/eprint/400053
ISSN: 0035-8711
PURE UUID: e527bf7d-e0d6-4c96-abcb-daf57dbed1b6
ORCID for P. Gandhi: ORCID iD orcid.org/0000-0003-3105-2615

Catalogue record

Date deposited: 09 Sep 2016 08:56
Last modified: 12 Nov 2019 01:35

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