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The 2-79 keV X-Ray Spectrum of the Circinus Galaxy with NuSTAR, XMM-Newton, and Chandra: A Fully Compton-thick Active Galactic Nucleus

Arèvalo, P. and Walton, D. J. and Fuerst, F. and Grefenstette, B. W. and Harrison, F. A. and Madsen, K. K. (2014) The 2-79 keV X-Ray Spectrum of the Circinus Galaxy with NuSTAR, XMM-Newton, and Chandra: A Fully Compton-thick Active Galactic Nucleus. Astrophysical Journal, 791 (2). Art. No. 81. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20140903-144941504

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Abstract

The Circinus galaxy is one of the closest obscured active galactic nuclei (AGNs), making it an ideal target for detailed study. Combining archival Chandra and XMM-Newton data with new NuSTAR observations, we model the 2-79 keV spectrum to constrain the primary AGN continuum and to derive physical parameters for the obscuring material. Chandra's high angular resolution allows a separation of nuclear and off-nuclear galactic emission. In the off-nuclear diffuse emission, we find signatures of strong cold reflection, including high equivalent-width neutral Fe lines. This Compton-scattered off-nuclear emission amounts to 18% of the nuclear flux in the Fe line region, but becomes comparable to the nuclear emission above 30 keV. The new analysis no longer supports a prominent transmitted AGN component in the observed band. We find that the nuclear spectrum is consistent with Compton scattering by an optically thick torus, where the intrinsic spectrum is a power law of photon index Γ = 2.2-2.4, the torus has an equatorial column density of N_H = (6-10) × 10^(24) cm^(–2), and the intrinsic AGN 2-10 keV luminosity is (2.3-5.1) × 10^(42) erg s^(–1). These values place Circinus along the same relations as unobscured AGNs in accretion rate versus Γ and L_X versus L_(IR) phase space. NuSTAR's high sensitivity and low background allow us to study the short timescale variability of Circinus at X-ray energies above 10 keV for the first time. The lack of detected variability favors a Compton-thick absorber, in line with the spectral fitting results.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://iopscience.iop.org/0004-637X/791/2/81PublisherArticle
http://dx.doi.org/10.1088/0004-637X/791/2/81DOIArticle
ORCID:
AuthorORCID
Harrison, F. A.0000-0003-2992-8024
Madsen, K. K.0000-0003-1252-4891
Additional Information:© 2014 American Astronomical Society. Received 2013 December 23; accepted 2014 June 11; published 2014 July 30. We thank the anonymous referee for a thorough review and many useful suggestions that improved this paper. This work was 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). We acknowledge financial support from Basal-CATA PFB-06/2007 (FEB), CONICYT-Chile FONDECYT 1140304 (PA), 1141218 (FEB), 1120061 (ET), and Anillo ACT1101 (PA, FEB, ET). A.C., A.M., and G.M. acknowledge the ASI-INAF grant I/037/12/0.W.N.B. and B.L. acknowledge support from Caltech NuSTAR subcontract 44A-1092750 and NASA ADP grant NNX10AC99G. M.K. gratefully acknowledges support from Swiss National Science Foundation Grant PP00P2_138979/1. P.G. thanks STFC for support (grant reference ST/J003697/1).
Group:NuSTAR, Space Radiation Laboratory
Funders:
Funding AgencyGrant Number
NASANNG08FD60C
NASA/JPL/CaltechUNSPECIFIED
Basal-CATAPFB-06/2007
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1140304
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1141218
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1120061
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)Anillo ACT1101
Agenzia Spaziale Italiana (ASI)I/037/12/0
Caltech NuSTAR subcontract44A-1092750
NASANNX10AC99G
Swiss National Science Foundation (SNSF)PP00P2_138979/1
Science and Technology Facilities Council (STFC) ST/J003697/1
Subject Keywords:galaxies: active; galaxies: individual (Circinus); galaxies: Seyfert; X-rays: galaxies
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2014-39
Record Number:CaltechAUTHORS:20140903-144941504
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140903-144941504
Official Citation:The 2-79 keV X-Ray Spectrum of the Circinus Galaxy with NuSTAR, XMM-Newton, and Chandra: A Fully Compton-thick Active Galactic Nucleus P. Arévalo et al. 2014 ApJ 791 81
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49208
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:04 Sep 2014 16:25
Last Modified:18 Nov 2016 00:55

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