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NuSTAR Spectroscopy of Multi-Component X-ray Reflection from NGC 1068

Bauer, Franz E. and Walton, Dominic J. and Baloković, Mislav and Brightman, Murray and Harrison, Fiona A. and Rivers, Elizabeth (2015) NuSTAR Spectroscopy of Multi-Component X-ray Reflection from NGC 1068. Astrophysical Journal, 812 (2). Art. No. 116. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20141203-100546034

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Abstract

We report on observations of NGC1068 with NuSTAR, which provide the best constraints to date on its > 10 keV spectral shape. The NuSTAR data are consistent with past instruments, with no strong continuum or line variability over the past two decades, consistent with its classification as a Compton-thick AGN. The combined NuSTAR, Chandra, XMM-Newton, and Swift BAT spectral dataset offers new insights into the complex secondary emission seen instead of the completely obscured transmitted nuclear continuum. The critical combination of the high signal-to-noise NuSTAR data and the decomposition of the nuclear and extranuclear emission with Chandra allow us to break several model degeneracies and greatly aid physical interpretation. When modeled as a monolithic (i.e., a single N_H) reflector, none of the common Compton-reflection models are able to match the neutral fluorescence lines and broad spectral shape of the Compton reflection without requiring unrealistic physical parameters (e.g., large Fe overabundances, inconsistent viewing angles, poor fits to the spatially resolved spectra). A multi-component reflector with three distinct column densities (e.g., with best-fit values of N_H = 1.5×10^(23), 5×10^(24), and 10^(25) cm^(-2)) provides a more reasonable fit to the spectral lines and Compton hump, with near-solar Fe abundances. In this model, the higher N_H component provides the bulk of the flux to the Compton hump while the lower N_H component produces much of the line emission, effectively decoupling two key features of Compton reflection. We also find that ≈ 30% of the neutral Fe Kɑ line flux arises from >2" (≈140 pc) and is clearly extended, implying that a significant fraction of the <10 keV reflected component arises from regions well outside of a parsec-scale torus. These results likely have ramifications for the interpretation of Compton-thick spectra from observations with poorer signal-to-noise and/or more distant objects.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://arxiv.org/abs/1411.0670arXivDiscussion Paper
http://dx.doi.org/10.1088/0004-637X/812/2/116DOIArticle
http://iopscience.iop.org/article/10.1088/0004-637X/812/2/116PublisherArticle
ORCID:
AuthorORCID
Bauer, Franz E.0000-0002-8686-8737
Walton, Dominic J.0000-0001-5819-3552
Harrison, Fiona A.0000-0003-2992-8024
Additional Information:© 2015 American Astronomical Society. Received 2014 November 3; accepted 2015 September 8; published 2015 October 14. We thank the anonymous referee for useful comments, which improved the clarity of the paper. We acknowledge financial support from the following: CONICYT-Chile Basal-CATA PFB-06/2007 (FEB, ET), FONDECYT grants 1141218 (FEB), 1140304 (PA), 1120061 (ET), and Anillo grant ACT1101 (FEB, PA, ET); Project IC120009 "Millennium Institute of Astrophysics (MAS)" funded by the Iniciativa Científica Milenio del Ministerio de Economía, Fomento y Turismo (FEB); Swiss National Science Foundation through the Ambizione fellowship grant PZ00P2_154799/1 (MK); NuSTAR subcontract 44A-1092750 NASA ADP grant NNX10AC99G (WNB, BL); ASI/INAF grant I/037/12/0–011/13 (SP, AC, AM and GM); and STFC grant ST/J003697/1 (PG). 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). This research has made use of data obtained through the High Energy Astrophysics Science Archive Research Center (HEASARC) Online Service, provided by the NASA/Goddard Space Flight Center. Facilities: CXO (ACIS, HETG), XMM (pn, MOS), NuSTAR (FPMA, FPMB), Swift (XRT, BAT), BeppoSAX (MECS, PDS), Suzaku (XIS, PIN),
Group:Space Radiation Laboratory, NuSTAR
Funders:
Funding AgencyGrant Number
NASANNG08FD60C
NASA/Caltech/JPLUNSPECIFIED
Basal-CATAPFB-06/2007
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1141218
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1140304
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1120061
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)Anillo ACT1101
Iniciativa Científica Milenio del Ministerio de Economía, Fomento y TurismoProject IC120009 “Millennium Institute of Astrophysics (MAS)”
Swiss National Science Foundation (SNSF)PZ00P2_154799/1
NuSTAR44A-1092750
NASANNX10AC99G
Agenzia Spaziale Italiana (ASI)I/037/12/0–011/13
Science and Technology Facilities Council (STFC) ST/J003697/1
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Subject Keywords:Galaxies: active, galaxies: individual (NGC 1068), X-rays: galaxies
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2015-26
Record Number:CaltechAUTHORS:20141203-100546034
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20141203-100546034
Official Citation:Franz E. Bauer et al 2015 ApJ 812 116
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:52317
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:03 Dec 2014 19:47
Last Modified:30 Nov 2017 22:10

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