THE NuSTAR EXTRAGALACTIC SURVEY: A FIRST SENSITIVE LOOK AT THE HIGH-ENERGY COSMIC X-RAY BACKGROUND POPULATION
- Department of Physics, Durham University, Durham DH1 3LE (United Kingdom)
- Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 169-221, Pasadena, CA 91109 (United States)
- Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)
- Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States)
- Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile)
- Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States)
- DTU Space-National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark)
- Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States)
- INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Cahill Center for Astrophysics, 1216 East California Boulevard, California Institute of Technology, Pasadena, CA 91125 (United States)
- Columbia Astrophysics Laboratory, 550 W 120th Street, Columbia University, NY 10027 (United States)
We 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 {approx}> 10 keV. We find that these NuSTAR-detected sources are Almost-Equal-To 100 times fainter than those previously detected at {approx}> 10 keV and have a broad range in redshift and luminosity (z = 0.020-2.923 and L{sub 10-40{sub keV}} Almost-Equal-To 4 Multiplication-Sign 10{sup 41}-5 Multiplication-Sign 10{sup 45} erg s{sup -1}); the median redshift and luminosity are z Almost-Equal-To 0.7 and L{sub 10-40{sub keV}} Almost-Equal-To 3 Multiplication-Sign 10{sup 44} erg s{sup -1}, respectively. We characterize these sources on the basis of broad-band Almost-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{sub keV}} > 10{sup 44} erg s{sup -1}, of which Almost-Equal-To 50% are obscured with N{sub H} {approx}> 10{sup 22} cm{sup -2}. However, none of the 10 NuSTAR sources are Compton thick (N{sub H} {approx}> 10{sup 24} cm{sup -2}) and we place a 90% confidence upper limit on the fraction of Compton-thick quasars (L{sub 10-40{sub keV}} > 10{sup 44} erg s{sup -1}) selected at {approx}> 10 keV of {approx}< 33% over the redshift range z = 0.5-1.1. We jointly fitted the rest-frame Almost-Equal-To 10-40 keV data for all of the non-beamed sources with L{sub 10-40{sub keV}} > 10{sup 43} erg s{sup -1} to constrain the average strength of reflection; we find R < 1.4 for {Gamma} = 1.8, broadly consistent with that found for local active galactic nuclei (AGNs) observed at {approx}> 10 keV. We also constrain the host-galaxy masses and find a median stellar mass of Almost-Equal-To 10{sup 11} M{sub Sun }, a factor Almost-Equal-To 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.
- OSTI ID:
- 22131004
- Journal Information:
- Astrophysical Journal, Vol. 773, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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