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NuSTAR uncovers an extremely local compton-thick AGN in NGC 4968

NuSTAR uncovers an extremely local compton-thick AGN in NGC 4968
NuSTAR uncovers an extremely local compton-thick AGN in NGC 4968
We present the analysis of Chandra and NuSTAR spectra of NGC 4968, a local (D ~ 44 Mpc) 12 μm selected Seyfert 2 galaxy, enshrouded within Compton-thick layers of obscuring gas. We find no evidence of variability between the Chandra and NuSTAR observations (separated by 2 yr), nor between the two NuSTAR observations (separated by 10 months). Using self-consistent X-ray models, we rule out the scenario where the obscuring medium is nearly spherical and uniform, contradicting the results implied by the <10 keV Chandra spectrum. The line-of-sight column density, from intervening matter between the source and observer that intercepts the intrinsic active galactic nucleus (AGN) X-ray emission, is well within the Compton-thick regime, with a minimum column density of 2 × 1024 cm−2. The average global column density is high (>3 × 1023 cm−2), with both Compton-thick and Compton-thin solutions permitted, depending on the X-ray spectral model. The spectral models provide a range of intrinsic AGN continuum parameters and implied 2–10 keV luminosities (L 2–10 keV,intrinsic), where the higher end of L 2–10 keV,intrinsic is consistent with expectations from the 12 μm luminosity (L 2–10 keV,intrinisc ~ 7 × 1042 erg s−1). Compared with Compton-thick AGN previously observed by NuSTAR, NGC 4968 is among the most intrinsically X-ray luminous. However, despite its close proximity and relatively high intrinsic X-ray luminosity, it is undetected by the 105 month Swift-Burst Alert Telescope survey, underscoring the importance of multiwavelength selection for obtaining the most complete census of the most hidden black holes.
0004-637X
1-14
LaMassa, Stephanie M.
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Yaqoob, Tahir
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Boorman, Peter G.
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Tzanavaris, Panayiotis
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Levenson, N.A.
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Gandhi, Poshak
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Ptak, Andrew F.
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Heckman, Timothy G.
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LaMassa, Stephanie M.
b441530d-49d6-4b7d-967e-b2840198fe69
Yaqoob, Tahir
46e66bed-864f-44af-b6d7-e0df35e2dfdc
Boorman, Peter G.
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Tzanavaris, Panayiotis
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Levenson, N.A.
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Gandhi, Poshak
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Ptak, Andrew F.
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Heckman, Timothy G.
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LaMassa, Stephanie M., Yaqoob, Tahir, Boorman, Peter G., Tzanavaris, Panayiotis, Levenson, N.A., Gandhi, Poshak, Ptak, Andrew F. and Heckman, Timothy G. (2019) NuSTAR uncovers an extremely local compton-thick AGN in NGC 4968. Astrophysical Journal, 887 (2), 1-14. (doi:10.3847/1538-4357/ab552c/meta).

Record type: Article

Abstract

We present the analysis of Chandra and NuSTAR spectra of NGC 4968, a local (D ~ 44 Mpc) 12 μm selected Seyfert 2 galaxy, enshrouded within Compton-thick layers of obscuring gas. We find no evidence of variability between the Chandra and NuSTAR observations (separated by 2 yr), nor between the two NuSTAR observations (separated by 10 months). Using self-consistent X-ray models, we rule out the scenario where the obscuring medium is nearly spherical and uniform, contradicting the results implied by the <10 keV Chandra spectrum. The line-of-sight column density, from intervening matter between the source and observer that intercepts the intrinsic active galactic nucleus (AGN) X-ray emission, is well within the Compton-thick regime, with a minimum column density of 2 × 1024 cm−2. The average global column density is high (>3 × 1023 cm−2), with both Compton-thick and Compton-thin solutions permitted, depending on the X-ray spectral model. The spectral models provide a range of intrinsic AGN continuum parameters and implied 2–10 keV luminosities (L 2–10 keV,intrinsic), where the higher end of L 2–10 keV,intrinsic is consistent with expectations from the 12 μm luminosity (L 2–10 keV,intrinisc ~ 7 × 1042 erg s−1). Compared with Compton-thick AGN previously observed by NuSTAR, NGC 4968 is among the most intrinsically X-ray luminous. However, despite its close proximity and relatively high intrinsic X-ray luminosity, it is undetected by the 105 month Swift-Burst Alert Telescope survey, underscoring the importance of multiwavelength selection for obtaining the most complete census of the most hidden black holes.

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NuSTAR Uncovers an Extremely Local Compton-thick AGN in NGC 4968 - Accepted Manuscript
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Accepted/In Press date: 5 November 2019
e-pub ahead of print date: 18 December 2019
Published date: 20 December 2019
Additional Information: arXiv is AM

Identifiers

Local EPrints ID: 438006
URI: http://eprints.soton.ac.uk/id/eprint/438006
ISSN: 0004-637X
PURE UUID: 992edba3-6327-4903-a864-fe9a3a75acb2
ORCID for Peter G. Boorman: ORCID iD orcid.org/0000-0001-9379-4716
ORCID for Poshak Gandhi: ORCID iD orcid.org/0000-0003-3105-2615

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Date deposited: 26 Feb 2020 17:30
Last modified: 07 Oct 2020 02:06

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Contributors

Author: Stephanie M. LaMassa
Author: Tahir Yaqoob
Author: Peter G. Boorman ORCID iD
Author: Panayiotis Tzanavaris
Author: N.A. Levenson
Author: Poshak Gandhi ORCID iD
Author: Andrew F. Ptak
Author: Timothy G. Heckman

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