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A long hard-x-ray look at the dual active galactic nuclei of M51 with NuSTAR

A long hard-x-ray look at the dual active galactic nuclei of M51 with NuSTAR
A long hard-x-ray look at the dual active galactic nuclei of M51 with NuSTAR

We present a broadband X-ray spectral analysis of the M51 system, including the dual active galactic nuclei (AGNs) and several off-nuclear point sources. Using a deep observation by NuSTAR, new high-resolution coverage of M51b by Chandra, and the latest X-ray torus models, we measure the intrinsic X-ray luminosities of the AGNs in these galaxies. The AGN of M51a is found to be Compton-thick, and both AGNs have very low accretion rates (). The latter is surprising considering that the galaxies of M51 are in the process of merging, which is generally predicted to enhance nuclear activity. We find that the covering factor of the obscuring material in M51a is 0.26 ± 0.03, consistent with the local AGN obscured fraction at erg s-1. The substantial obscuring column does not support theories that the torus, presumed responsible for the obscuration, disappears at these low accretion luminosities. However, the obscuration may have resulted from the gas infall driven by the merger rather than the accretion process. We report on several extranuclear sources with erg s-1 and find that a spectral turnover is present below 10 keV in most such sources, in line with recent results on ultraluminous X-ray sources.

galaxies: active, galaxies: individual (M51), galaxies: nuclei, X-rays: binaries, X-rays: galaxies
0004-637X
Brightman, M.
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Baloković, M.
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Koss, M.
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Alexander, D. M.
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Annuar, A.
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Earnshaw, H.
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Gandhi, P.
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Harrison, F. A.
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Hornschemeier, A. E.
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Lehmer, B.
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Powell, M. C.
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Ptak, A.
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Rangelov, B.
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Roberts, T. P.
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Stern, D.
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Walton, D.J.
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Zezas, A.
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Brightman, M.
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Baloković, M.
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Koss, M.
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Alexander, D. M.
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Annuar, A.
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Earnshaw, H.
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Gandhi, P.
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Harrison, F. A.
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Hornschemeier, A. E.
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Lehmer, B.
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Powell, M. C.
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Ptak, A.
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Rangelov, B.
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Roberts, T. P.
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Stern, D.
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Walton, D.J.
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Zezas, A.
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Brightman, M., Baloković, M., Koss, M., Alexander, D. M., Annuar, A., Earnshaw, H., Gandhi, P., Harrison, F. A., Hornschemeier, A. E., Lehmer, B., Powell, M. C., Ptak, A., Rangelov, B., Roberts, T. P., Stern, D., Walton, D.J. and Zezas, A. (2018) A long hard-x-ray look at the dual active galactic nuclei of M51 with NuSTAR. The Astrophysical Journal, 867 (2), [110]. (doi:10.3847/1538-4357/aae1ae).

Record type: Article

Abstract

We present a broadband X-ray spectral analysis of the M51 system, including the dual active galactic nuclei (AGNs) and several off-nuclear point sources. Using a deep observation by NuSTAR, new high-resolution coverage of M51b by Chandra, and the latest X-ray torus models, we measure the intrinsic X-ray luminosities of the AGNs in these galaxies. The AGN of M51a is found to be Compton-thick, and both AGNs have very low accretion rates (). The latter is surprising considering that the galaxies of M51 are in the process of merging, which is generally predicted to enhance nuclear activity. We find that the covering factor of the obscuring material in M51a is 0.26 ± 0.03, consistent with the local AGN obscured fraction at erg s-1. The substantial obscuring column does not support theories that the torus, presumed responsible for the obscuration, disappears at these low accretion luminosities. However, the obscuration may have resulted from the gas infall driven by the merger rather than the accretion process. We report on several extranuclear sources with erg s-1 and find that a spectral turnover is present below 10 keV in most such sources, in line with recent results on ultraluminous X-ray sources.

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A Long Hard-X-Ray Look at the Dual Active Galactic Nuclei of M51 with NuSTAR - Accepted Manuscript
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Accepted/In Press date: 12 September 2018
e-pub ahead of print date: 5 November 2018
Published date: 10 November 2018
Additional Information: Author Ghandi, has confirmed that Arxiv record AM
Keywords: galaxies: active, galaxies: individual (M51), galaxies: nuclei, X-rays: binaries, X-rays: galaxies

Identifiers

Local EPrints ID: 426802
URI: http://eprints.soton.ac.uk/id/eprint/426802
ISSN: 0004-637X
PURE UUID: 2210c7c5-001f-447f-aff1-89ae6a873a37
ORCID for P. Gandhi: ORCID iD orcid.org/0000-0003-3105-2615

Catalogue record

Date deposited: 12 Dec 2018 17:30
Last modified: 17 Dec 2019 01:34

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Contributors

Author: M. Brightman
Author: M. Baloković
Author: M. Koss
Author: D. M. Alexander
Author: A. Annuar
Author: H. Earnshaw
Author: P. Gandhi ORCID iD
Author: F. A. Harrison
Author: A. E. Hornschemeier
Author: B. Lehmer
Author: M. C. Powell
Author: A. Ptak
Author: B. Rangelov
Author: T. P. Roberts
Author: D. Stern
Author: D.J. Walton
Author: A. Zezas

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