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Testing a double AGN hypothesis for Mrk 273

Iwasawa, K. and U, V. and Mazzarella, J. M. and Medling, A. M. and Sanders, D. B. and Evans, A. S. (2018) Testing a double AGN hypothesis for Mrk 273. Astronomy and Astrophysics, 611 . Art. No. A71. ISSN 0004-6361.

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The ultra-luminous infrared galaxy (ULIRG) Mrk 273 contains two infrared nuclei, N and SW, separated by 1 arcsecond. A Chandraobservation has identified the SW nucleus as an absorbed X-ray source with N_H ~ 4 × 10^(23) cm^(−2) but also hinted at the possible presence of a Compton-thick AGN in the N nucleus, where a black hole of ~10^9 M⊙ is inferred from the ionized gas kinematics. The intrinsic X-ray spectral slope recently measured by NuSTAR is unusually hard (Γ ~ 1.3) for a Seyfert nucleus, for which we seek an alternative explanation. We hypothesize a strongly absorbed X-ray source in N, of which X-ray emission rises steeply above 10 keV, in addition to the known X-ray source in SW, and test it against the NuSTAR data, assuming the standard spectral slope (Γ = 1.9). This double X-ray source model gives a good explanation of the hard continuum spectrum, deep Fe K absorption edge, and strong Fe K line observed in this ULIRG, without invoking the unusual spectral slope required for a single source interpretation. The putative X-ray source in N is found to be absorbed by N_H = 1.4^(+0.7)_(−0.4) × 10^(24) cm^(−2). The estimated 2−10 keV luminosity of the N source is 1.3 × 10^(43) erg s^(−1), about a factor of 2 larger than that of SW during the NuSTAR observation. Uncorrelated variability above and below 10 keV between the Suzaku and NuSTAR observations appears to support the double source interpretation. Variability in spectral hardness and Fe K line flux between the previous X-ray observations is also consistent with this picture.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Iwasawa, K.0000-0002-4923-3281
U, V.0000-0002-1912-0024
Mazzarella, J. M.0000-0002-8204-8619
Medling, A. M.0000-0001-7421-2944
Sanders, D. B.0000-0002-1233-9998
Evans, A. S.0000-0003-2638-1334
Additional Information:© 2018 ESO. Article published by EDP Sciences. Received 27 July 2017; Accepted 4 November 2017; Published online 02 April 2018. This research made use of data obtained from NuSTAR, Chandra X-ray Observatory, XMM-Newton and Suzaku, reduced and analysed by software provided by HEASARC, the Chandra X-ray Center, and the XMM-Newton Science Operation Centre. K.I. acknowledges support by the Spanish MINECO under grant AYA2016-76012-C3-1-P and MDM-2014-0369 of ICCUB (Unidad de Excelencia “María de Maeztu”). V.U. acknowledges funding support from the University of California Chancellor’s Postdoctoral Fellowship. Support for AMM is provided by NASA through Hubble Fellowship grant #HST-HF2-51377 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
University of CaliforniaUNSPECIFIED
NASA Hubble FellowshipHST-HF2-51377
Ministerio de Economía, Industria y Competitividad (MINECO)AYA2016-76012-C3-1-P
Ministerio de Economía, Industria y Competitividad (MINECO)MDM-2014-0369
Subject Keywords:galaxies: nuclei – X-rays: galaxies
Record Number:CaltechAUTHORS:20180502-155832466
Persistent URL:
Official Citation:Testing a double AGN hypothesis for Mrk 273 K. Iwasawa, V. U, J. M. Mazzarella, A. M. Medling, D. B. Sanders and A. S. Evans A&A, 611 (2018) A71 DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86202
Deposited By: Tony Diaz
Deposited On:03 May 2018 20:24
Last Modified:09 Mar 2020 13:18

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