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X-ray fluorescent lines from the Compton-thick AGN in M51

Xu, Weiwei and Liu, Zhu and Gou, Lijun and Liu, Jiren (2016) X-ray fluorescent lines from the Compton-thick AGN in M51. Monthly Notices of the Royal Astronomical Society: Letters, 455 (1). L26-L30. ISSN 1745-3925.

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The cold disc/torus gas surrounding active galactic nuclei (AGN) emits fluorescent lines when irradiated by hard X-ray photons. The fluorescent lines of elements other than Fe and Ni are rarely detected due to their relative faintness. We report the detection of Kα lines of neutral Si, S, Ar, Ca, Cr, and Mn, along with the prominent Fe Kα, Fe Kβ, and Ni Kα lines, from the deep Chandra observation of the low-luminosity Compton-thick AGN in M51. The Si Kα line at 1.74 keV is detected at ∼3σ, the other fluorescent lines have a significance between 2 and 2.5 σ, while the Cr line has a significance of ∼1.5σ. These faint fluorescent lines are made observable due to the heavy obscuration of the intrinsic spectrum of M51, which is revealed by NuSTAR observation above 10 keV. The hard X-ray continuum of M51 from Chandra and NuSTAR can be fitted with a power-law spectrum with an index of 1.8, reprocessed by a torus with an equatorial column density of NH ∼ 7 × 10^(24) cm^(−2) and an inclination angle of 74°. This confirms the Compton-thick nature of the nucleus of M51. The relative element abundances inferred from the fluxes of the fluorescent lines are similar to their solar values, except for Mn, which is about 10 times overabundant. It indicates that Mn is likely enhanced by the nuclear spallation of Fe.

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Liu, Zhu0000-0002-8968-7050
Additional Information:© 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2015 September 29. Received 2015 September 28. In original form 2015 August 3. First published online October 20, 2015. We thank our referee for valuable comments. JL is supported by NSFC grant 11203032, and LG is supported by the Strategic Priority Research Program ‘The Emergence of Cosmological Structures’ of CAS grant XDB09000000, NSFC grant 11333005, and NAOC grant Y234031001. This research is based on data obtained from the Chandra Data Archive and uses data from NuSTAR mission.
Funding AgencyGrant Number
National Science Foundation of China11203032
Chinese Academy of SciencesXDB09000000
National Science Foundation of China11333005
National Astronomical Observatories, Chinese Academy of Sciences (NAOC)Y234031001
Subject Keywords:atomic processes – galaxies: individual: M51 (NGC 5194) – galaxies: Seyfert – X-rays: galaxies
Issue or Number:1
Record Number:CaltechAUTHORS:20160204-181822135
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Official Citation:Weiwei Xu, Zhu Liu, Lijun Gou, and Jiren Liu X-ray fluorescent lines from the Compton-thick AGN in M51 MNRAS (January 01, 2016) Vol. 455 L26-L30 doi:10.1093/mnrasl/slv148 First published online October 20, 2015
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64254
Deposited By: Joy Painter
Deposited On:05 Feb 2016 17:32
Last Modified:09 Mar 2020 13:19

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