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A Long Hard-X-Ray Look at the Dual Active Galactic Nuclei of M51 with NuSTAR

Brightman, M. and Baloković, M. and Koss, M. and Alexander, D. M. and Annuar, A. and Earnshaw, H. P. and Gandhi, P. and Harrison, F. A. and Hornschemeier, A. E. and Lehmer, B. and Powell, M. C. and Ptak, A. and Rangelov, B. and Roberts, T. P. and Stern, D. and Walton, D. J. and Zezas, A. (2018) A Long Hard-X-Ray Look at the Dual Active Galactic Nuclei of M51 with NuSTAR. Astrophysical Journal, 867 (2). Art. No. 110. ISSN 1538-4357. doi:10.3847/1538-4357/aae1ae.

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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 (λ_Edd) < 10^(-4)). 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 L_X ~10^(40) 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 L_X > 10^(-39) 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Brightman, M.0000-0002-8147-2602
Baloković, M.0000-0003-0476-6647
Koss, M.0000-0002-7998-9581
Alexander, D. M.0000-0002-5896-6313
Annuar, A.0000-0003-0387-1429
Earnshaw, H. P.0000-0001-5857-5622
Gandhi, P.0000-0003-3105-2615
Harrison, F. A.0000-0003-2992-8024
Hornschemeier, A. E.0000-0001-8667-2681
Lehmer, B.0000-0003-2192-3296
Powell, M. C.0000-0003-2284-8603
Ptak, A.0000-0001-5655-1440
Rangelov, B.0000-0002-9282-5207
Roberts, T. P.0000-0001-8252-6337
Stern, D.0000-0003-2686-9241
Walton, D. J.0000-0001-5819-3552
Zezas, A.0000-0001-8952-676X
Additional Information:© 2018 The American Astronomical Society. Received 2018 May 29; revised 2018 September 6; accepted 2018 September 12; published 2018 November 5. The authors thank the anonymous referee for the thorough and detailed review of our manuscript, which improved it. M. Baloković acknowledges support from the Black Hole Initiative at Harvard University, through the grant from the John Templeton Foundation. M.K. acknowledges support from NASA through ADAP award NNH16CT03C. D.M.A. acknowledges the Science and Technology Facilities Council (STFC) through grant ST/P000541/1. The work of D.S. was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. A.Z. acknowledges funding from the European Research Council under the European Unions Seventh Framework Programme (FP/2007–2013)/ERC Grant Agreement n. 617001. Support for this work was provided by the National Aeronautics and Space Administration through Chandra Award Number GO7-18105X issued by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics Space Administration under contract NAS8-03060. This work was also supported under NASA contract No. NNG08FD60C, and made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. We thank the NuSTAR Operations, Software, and Calibration teams for support with the execution and analysis of these observations. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA). Facilities: Chandra (ACIS) - , NuSTAR - , Hale (DBSP) - .
Group:NuSTAR, Space Radiation Laboratory, Astronomy Department
Funding AgencyGrant Number
Harvard UniversityUNSPECIFIED
John Templeton FoundationUNSPECIFIED
Science and Technology Facilities Council (STFC)ST/P000541/1
European Research Council (ERC)617001
Subject Keywords:galaxies: active – galaxies: individual (M51) – galaxies: nuclei – X-rays: binaries – X-rays: galaxies
Issue or Number:2
Record Number:CaltechAUTHORS:20181106-105511630
Persistent URL:
Official Citation:M. Brightman et al 2018 ApJ 867 110
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:90668
Deposited By: Tony Diaz
Deposited On:06 Nov 2018 21:59
Last Modified:16 Nov 2021 03:34

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