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NuSTAR and XMM-Newton Observations of Luminous, Heavily Obscured, WISE-selected Quasars at z ~ 2

Stern, Daniel and Lansbury, G. B. and Assef, R. J. and Brandt, W. N. and Alexander, D. M. and Ballantyne, D. R. and Baloković, M. and Bauer, F. E. and Benford, D. and Blain, A. and Boggs, S. E. and Bridge, C. and Brightman, M. and Christensen, F. E. and Comastri, Andrea and Craig, William W. and Del Moro, A. and Eisenhardt, Peter R. M. and Gandhi, P. and Griffith, R. L. and Hailey, C. J. and Harrison, F. A. and Hickox, R. C. and Jarrett, T. H. and Koss, M. and Lake, S. and LaMassa, S. M. and Luo, B. and Tsai, C.-W. and Urry, C. M. and Walton, D. J. and Wright, D. J. and Wu, J. and Yan, L. and Zhang, W. W. (2014) NuSTAR and XMM-Newton Observations of Luminous, Heavily Obscured, WISE-selected Quasars at z ~ 2. Astrophysical Journal, 79 (2). Art No.102. ISSN 0004-637X.

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We report on a NuSTAR and XMM-Newton program that has observed a sample of three extremely luminous, heavily obscured WISE-selected active galactic nuclei (AGNs) at z ~ 2 across a broad X-ray band (0.1 - 79 keV). The parent sample, selected to be faint or undetected in the WISE 3.4 μm (W1) and 4.6 μm (W2) bands but bright at 12 μm (W3) and 22 μm (W4), are extremely rare, with only ~1000 so-called "W1W2-dropouts" across the extragalactic sky. Optical spectroscopy reveals typical redshifts of z ~ 2 for this population, implying rest-frame mid-IR luminosities of νL ν(6 μm) ~ 6 × 1046 erg s^-1 and bolometric luminosities that can exceed L bol ~ 1014 L_⊙. The corresponding intrinsic, unobscured hard X-ray luminosities are L(2-10 keV) ~ 4 × 1045 erg s-1 for typical quasar templates. These are among the most AGNs known, though the optical spectra rarely show evidence of a broad-line region and the selection criteria imply heavy obscuration even at rest-frame 1.5 μm. We designed our X-ray observations to obtain robust detections for gas column densities N H <= 1024 cm-2. In fact, the sources prove to be fainter than these predictions. Two of the sources were observed by both NuSTAR and XMM-Newton, with neither being detected by NuSTAR (f 3-24 keV <~ 10-13 erg cm^(-2)s^(-1), and one being faintly detected by XMM-Newton (f 0.5-10 keV ~ 5 × 10-15 erg cm-2 s-1). A third source was observed only with XMM-Newton, yielding a faint detection (f 0.5-10 keV ~ 7 × 10-15 erg cm-2 s-1). The X-ray data imply these sources are either X-ray weak, or are heavily obscured by column densities N H >~ 1024 cm-2. The combined X-ray and mid-IR analysis seems to favor this second possibility, implying the sources are extremely obscured, consistent with Compton-thick, luminous quasars. The discovery of a significant population of heavily obscured, extremely luminous AGNs would not conform to the standard paradigm of a receding torus, in which more luminous quasars are less likely to be obscured, and instead suggests that an additional source of obscuration is present in these extreme sources.

Item Type:Article
Related URLs:
URLURL TypeDescription
Stern, Daniel0000-0003-2686-9241
Lansbury, G. B.0000-0002-5328-9827
Assef, R. J.0000-0002-9508-3667
Brandt, W. N.0000-0002-0167-2453
Alexander, D. M.0000-0002-5896-6313
Ballantyne, D. R.0000-0001-8128-6976
Bauer, F. E.0000-0002-8686-8737
Boggs, S. E.0000-0001-9567-4224
Comastri, Andrea0000-0003-3451-9970
Gandhi, P.0000-0003-3105-2615
Harrison, F. A.0000-0003-2992-8024
Koss, M.0000-0002-7998-9581
Luo, B.0000-0002-9036-0063
Urry, C. M.0000-0002-0745-9792
Yan, L.0000-0003-1710-9339
Additional Information:© 2014. The American Astronomical Society. Published 2014 September 29. We gratefully acknowledge the suggestions made by the anonymous referee, which have improved this manuscript. 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 publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. We acknowledge financial support from the Science and Technology Facilities Council (STFC) grants ST/K501979/1 (G.B.L.), ST/I001573/1 (D.M.A. and A.D.M.), and ST/J003697/1 (P.G.), and the Leverhulme Trust (D.M.A. and J.R.M.). R.J.A. was supported by Gemini-CONICYT grant number 32120009. F.E.B. acknowledges support from CONICYT-Chile (Basal-CATA PFB-06/2007, FONDECYT 1141218, and “EMBIGGEN” Anillo ACT1101) and Project IC120009 “Millennium Institute of Astrophysics (MAS)” of Iniciativa Cient´ıfica Milenio del Ministerio de Econom´ıa, Fomento y Turismo. A.C. acknowledges support from ASI-INAF grant I/37/012/0-011/13. R.C.H. acknowledges support from NASA through ADAP award NNX12AE38G and the National Science Foundation through grant number 1211096. M.K. acknowledges support from Swiss National Science Foundation (NSF) grant PP00P2 138979/1.
Group:Space Radiation Laboratory, NuSTAR, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)ST/K501979/1
Science and Technology Facilities Council (STFC)ST/J003697/1
Leverhulme TrustUNSPECIFIED
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)32120009
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1141218
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)EMBIGGEN Anillo ACT1101
Iniciativa Científica Milenio (ICM) del Ministerio de EconomíaIC120009
Agenzia Spaziale Italiana (ASI)I/37/012/0-011/13
Swiss Science Foundation (SNSF)PP00P2138979/1
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2014-28
Record Number:CaltechAUTHORS:20160824-144504856
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:69914
Deposited By: Deborah Miles
Deposited On:07 Sep 2016 03:45
Last Modified:21 Mar 2019 19:01

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