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NuSTAR J033202-2746.8: Direct Constraints on the Compton Reflection in a Heavily Obscured Quasar at z ≈ 2

Del Moro, A. and Baloković, M. and Harrison, F. A. (2014) NuSTAR J033202-2746.8: Direct Constraints on the Compton Reflection in a Heavily Obscured Quasar at z ≈ 2. Astrophysical Journal, 786 (1). Art. No. 16. ISSN 0004-637X.

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We report Nuclear Spectroscopic Telescope Array (NuSTAR) observations of NuSTAR J033202-2746.8, a heavily obscured, radio-loud quasar detected in the Extended Chandra Deep Field-South, the deepest layer of the NuSTAR extragalactic survey (~400 ks, at its deepest). NuSTAR J033202-2746.8 is reliably detected by NuSTAR only at E > 8 keV and has a very flat spectral slope in the NuSTAR energy band (Γ = 0.55^(+0.62)_(-0.64); 3-30 keV). Combining the NuSTAR data with extremely deep observations by Chandra and XMM-Newton (4 Ms and 3 Ms, respectively), we constrain the broad-band X-ray spectrum of NuSTAR J033202-2746.8, indicating that this source is a heavily obscured quasar (N_H = 5.6^(+0.9)_(-0.8) x 10^(23) cm^(–2)) with luminosity L_(10-40 keV) ≈6.4 × 10^(44) erg s^(–1). Although existing optical and near-infrared (near-IR) data, as well as follow-up spectroscopy with the Keck and VLT telescopes, failed to provide a secure redshift identification for NuSTAR J033202-2746.8, we reliably constrain the redshift z = 2.00 ± 0.04 from the X-ray spectral features (primarily from the iron K edge). The NuSTAR spectrum shows a significant reflection component (R = 0.55^(0.44)_(-0.37)), which was not constrained by previous analyses of Chandra and XMM-Newton data alone. The measured reflection fraction is higher than the R ~ 0 typically observed in bright radio-loud quasars such as NuSTAR J033202-2746.8, which has L_(1.4 GHz) ≈10^(27) W Hz^(–1). Constraining the spectral shape of active galactic nuclei (AGNs), including bright quasars, is very important for understanding the AGN population, and can have a strong impact on the modeling of the X-ray background. Our results show the importance of NuSTAR in investigating the broad-band spectral properties of quasars out to high redshift.

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Additional Information:© 2014 The American Astronomical Society. Received 2013 December 23; accepted 2014 March 9; published 2014 April 10. We thank the anonymous referee for careful reading and for the helpful comments, which helped improving this manuscript. We gratefully acknowledge financial support from the UK Science and Technology Facilities Council (STFC, ST/I001573/I, ADM and DMA; ST/K501979/1, GBL; ST/J003697/1, PG) and the Leverhulme Trust (D.M.A. and J.R.M.). A.C., C.V., R.G., and P.R. thank the ASI/INAF grant I/037/12/0-011/ 13. F.E.B. acknowledges support from Basal-CATA (PFB-06/ 2007) and CONICYT-Chile (FONDECYT 1101024 and Anillo grant ACT1101) and E.T. acknowledges the FONDECYT grant 1120061. W.N.B. and B.L. thank Caltech NuSTAR subcontract 44A-1092750 and NASA ADP grant NNX10AC99G. M.B. acknowledges the International Fulbright Science and Technology Award. 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 work also used observations made with ESO Telescopes at the La Silla Paranal Observatory under the program ID 092.A-0452.
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)ST/I001573/I
Science and Technology Facilities Council (STFC) ST/K501979/1
Science and Technology Facilities Council (STFC) ST/J003697/1
Leverhulme TrustUNSPECIFIED
CONICYT-ChileAnillo ACT1101
FONDECYT 1120061
Caltech NuSTAR subcontract44A-1092750
International Fulbright Science and Technology AwardUNSPECIFIED
Subject Keywords:galaxies: active; infrared: galaxies; quasars: general; quasars: individual (NuSTAR J033202-2746.8); X-rays: galaxies
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Space Radiation Laboratory2014-58
Record Number:CaltechAUTHORS:20140617-132453849
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Official Citation:NuSTAR J033202-2746.8: Direct Constraints on the Compton Reflection in a Heavily Obscured Quasar at z 2 A. Del Moro et al. 2014 ApJ 786 16
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46309
Deposited By: Tony Diaz
Deposited On:17 Jun 2014 22:44
Last Modified:09 Sep 2016 20:34

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