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The NuSTAR Serendipitous Survey: Hunting for the Most Extreme Obscured AGN at >10 keV

Lansbury, G. B. and Baloković, M. and Brightman, M. and Harrison, F. A. and Walton, D. J. (2017) The NuSTAR Serendipitous Survey: Hunting for the Most Extreme Obscured AGN at >10 keV. Astrophysical Journal, 846 (1). Art. No. 20. ISSN 0004-637X.

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We identify sources with extremely hard X-ray spectra (i.e., with photon indices of Γ ≾ 0.6) in the 13 deg^2 NuSTAR serendipitous survey, to search for the most highly obscured active galactic nuclei (AGNs) detected at > 10 keV. Eight extreme NuSTAR sources are identified, and we use the NuSTARdata in combination with lower-energy X-ray observations (from Chandra, Swift XRT, and XMM-Newton) to characterize the broadband (0.5–24 keV) X-ray spectra. We find that all of the extreme sources are highly obscured AGNs, including three robust Compton-thick (CT; N_H > 1.5 x 10^(24) cm^(−2)) AGNs at low redshift (z < 0.1) and a likely CT AGN at higher redshift (z = 0.16). Most of the extreme sources would not have been identified as highly obscured based on the low-energy (< 10 keV) X-ray coverage alone. The multiwavelength properties (e.g., optical spectra and X-ray–mid-IR luminosity ratios) provide further support for the eight sources being significantly obscured. Correcting for absorption, the intrinsic rest-frame 10–40 keV luminosities of the extreme sources cover a broad range, from ≈5 x 10^(42) to 10^(45) erg s^(−1). The estimated number counts of CT AGNs in the NuSTARserendipitous survey are in broad agreement with model expectations based on previous X-ray surveys, except for the lowest redshifts (z < 0.07), where we measure a high CT fraction of f^(obs)_(CT) = 30^(+16)_(-12)%. For the small sample of CT AGNs, we find a high fraction of galaxy major mergers (50% ± 33%) compared to control samples of "normal" AGNs.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Lansbury, G. B.0000-0002-5328-9827
Baloković, M.0000-0003-0476-6647
Brightman, M.0000-0002-8147-2602
Harrison, F. A.0000-0003-2992-8024
Walton, D. J.0000-0001-5819-3552
Additional Information:© 2017 The American Astronomical Society. Received 2017 March 10; revised 2017 July 19; accepted 2017 July 19; published 2017 August 28. The authors first thank the anonymous referee for the positive and constructive review. We acknowledge support from a Herchel Smith Postdoctoral Research Fellowship of the University of Cambridge (G.B.L.); the Science and Technology Facilities Council (STFC) grants ST/I001573/1 (D.M.A.) and ST/J003697/2 (P.G.); the ERC Advanced Grant FEEDBACK 340442 at the University of Cambridge (J.A.); the NASA Earth and Space Science Fellowship Program, grant NNX14AQ07H (M.B.); CONICYT-Chile grants FONDECYT Regular 1141218 (F.E.B.), FONDECYT 1120061 and 1160999 (E.T.), and Anillo ACT1101 (F.E.B. and E.T.); the Center of Excellence in Astrophysics and Associated Technologies (PFB 06; F.E.B. and E.T.); the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to the Millennium Institute of Astrophysics, MAS (F.E.B.); ASI/INAF contract I/037/12/0-011/13 (A.C., A.M., and L.Z.); and Chandra grants GO5-16154X and GO6-17135X (J.A.T.). We thank Yoshihiro Ueda and Roberto Gilli for providing number counts predictions. 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). Facilities: Chandra - , ESO La Silla - , Keck - , Magellan - , NuSTAR - , Palomar - , Pan-STARRS - , SDSS - , Swift - , WISE - , XMM-Newton.
Group:NuSTAR, Space Radiation Laboratory, Astronomy Department
Funding AgencyGrant Number
University of CambridgeUNSPECIFIED
Science and Technology Facilities Council (STFC)ST/I001573/1
Science and Technology Facilities Council (STFC)ST/J003697/2
European Research Council (ERC)340442
NASA Earth and Space Science FellowshipNNX14AQ07H
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1141218
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1120061
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1160999
Consejo Nacional de Ciencia y Tecnología (CONACYT)Anillo ACT1101
Center of Excellence in Astrophysics and Associated Technologies (CATA)PFB 06
Iniciativa Científica Milenio del Ministerio de Economía, Fomento y TurismoIC120009
Agenzia Spaziale Italiana (ASI)I/037/12/0-011/13
Subject Keywords:galaxies: active – galaxies: nuclei – quasars: general – surveys – X-rays: galaxies
Issue or Number:1
Record Number:CaltechAUTHORS:20170829-101443114
Persistent URL:
Official Citation:G. B. Lansbury et al 2017 ApJ 846 20
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:80896
Deposited By: Tony Diaz
Deposited On:29 Aug 2017 19:23
Last Modified:15 Nov 2019 04:55

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