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The NuSTAR Extragalactic Survey: A First Sensitive Look at the High-Energy Cosmic X-Ray Background PopulationWe report on the first 10 identifications of sources serendipitously detected by the Nuclear Spectroscopic Telescope Array (NuSTAR) to provide the first sensitive census of the cosmic X-ray background source population at approximately greater than 10 keV. We find that these NuSTAR-detected sources are approximately 100 times fainter than those previously detected at approximately greater than 10 keV and have a broad range in redshift and luminosity (z = 0.020-2.923 and L(sub 10-40 keV) approximately equals 4 × 10(exp 41) - 5 × 10(exp 45) erg per second; the median redshift and luminosity are z approximately equal to 0.7 and L(sub 10-40 keV) approximately equal to 3 × 10(exp 44) erg per second, respectively. We characterize these sources on the basis of broad-band approximately equal to 0.5 - 32 keV spectroscopy, optical spectroscopy, and broad-band ultraviolet-to-mid-infrared spectral energy distribution analyses. We find that the dominant source population is quasars with L(sub 10-40 keV) greater than 10(exp 44) erg per second, of which approximately 50% are obscured with N(sub H) approximately greater than 10(exp 22) per square centimeters. However, none of the 10 NuSTAR sources are Compton thick (N(sub H) approximately greater than 10(exp 24) per square centimeters) and we place a 90% confidence upper limit on the fraction of Compton-thick quasars (L(sub 10-40 keV) greater than 10(exp 44) erg per second) selected at approximately greater than 10 keV of approximately less than 33% over the redshift range z = 0.5 - 1.1. We jointly fitted the rest-frame approximately equal to 10-40 keV data for all of the non-beamed sources with L(sub 10-40 keV) greater than 10(exp 43) erg per second to constrain the average strength of reflection; we find R less than 1.4 for gamma = 1.8, broadly consistent with that found for local active galactic nuclei (AGNs) observed at approximately greater than 10 keV. We also constrain the host-galaxy masses and find a median stellar mass of approximately 10(exp 11) solar mass, a factor approximately 5 times higher than the median stellar mass of nearby high-energy selected AGNs, which may be at least partially driven by the order of magnitude higher X-ray luminosities of the NuSTAR sources. Within the low source-statistic limitations of our study, our results suggest that the overall properties of the NuSTAR sources are broadly similar to those of nearby high-energy selected AGNs but scaled up in luminosity and mass.
Document ID
20140017786
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
doi:10.1088/0004-637X/773/2/125
Authors
Alexander, D. M. (Durham Univ. United Kingdom)
Stern, D. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
DelMoro, A. (Durham Univ. United Kingdom)
Lansbury, G. B. (Durham Univ. United Kingdom)
Assef, R. J. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Aird, J. (Durham Univ. United Kingdom)
Ajello, M. (California Univ. Berkeley, CA, United States)
Ballantyne, D. R. (Georgia Inst. of Tech. Atlanta, GA, United States)
Bauer, F. E. (Pontificia Univ. Catolica de Chile Santiago, Chile)
Boggs, S. E. (California Univ. Berkeley, CA, United States)
Brandt, W. N. (Pennsylvania State Univ. University Park, PA, United States)
Christensen, F. E. (Technical Univ. of Denmark Lyngby, Denmark)
Civano, F. (Dartmouth Coll. Hanover, NH, United States)
Cosmastri, A. (Osservatorio Astronomico Bologna, Italy)
Craig, W. W. (Technical Univ. of Denmark Lyngby, Denmark)
Elvis, M. (Harvard-Smithsonian Center for Astrophysics Cambridge, MA, United States)
Grefenstette, B. W. (California Inst. of Tech. Pasadena, CA, United States)
Hailey, C. J. (Columbia Univ. New York, NY, United States)
Harrison, F. A. (California Inst. of Tech. Pasadena, CA, United States)
Hickox, R. C. (Dartmouth Coll. Hanover, NH, United States)
Luo, B. (Pennsylvania State Univ. University Park, PA, United States)
Madsen, K. K. (California Inst. of Tech. Pasadena, CA, United States)
Alexander, D. M. (Durham Univ. United Kingdom)
Zhang, W. W. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Eisenhardt, P. R. M. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
December 30, 2014
Publication Date
August 1, 2013
Publication Information
Publication: The Astrophysical Journal
Publisher: The Astrophysical Journal
Volume: 773
Issue: 2
Subject Category
Astronomy
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN11750
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
Spectroscopic
Telescope
Nuclear

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