The NuSTAR extragalactic survey: First direct measurements of the ≳10 keV X-ray luminosity function for active galactic nuclei at z > 0.1

Journal Article · Thu Dec 10 04:00:00 EST 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/815/1/66· OSTI ID:22882337

Aird, J.; Fabian, A. C. ^[1]; Alexander, D. M.; Del-Moro, A.; Lansbury, G. B.; Gandhi, P. ^[2]; Ballantyne, D. R. ^[3]; Civano, F. ^[4]; Hickox, R. C. ^[5]; Mullaney, J. R. ^[6]; Bauer, F. E. ^[7]; Brandt, W. N.; Luo, B. ^[8]; Comastri, A. ^[9]; Harrison, F. A. ^[10]; Stern, D. ^[11]; Treister, E. ^[12]; others, and

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1. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA (United Kingdom)
2. Centre of Extragalactic Astronomy, Department of Physics, Durham University, Durham, DH1 3LE (United Kingdom)
3. Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States)
4. Yale Center for Astronomy and Astrophysics, 260 Whitney Avenue, New Haven, CT 06520 (United States)
5. Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States)
6. The Department of Physics and Astronomy, The University of Sheffield, Hounsfield Road, Sheffield S3 7RH (United Kingdom)
7. Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Catòlica de Chile, 306, Santiago 22 (Chile)
8. Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States)
9. INAF Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127, Bologna (Italy)
10. Cahill Center for Astrophysics, California Institute of Technology, 1216 E. California Boulevard, Pasadena, CA 91125 (United States)
11. Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 169-221, Pasadena, CA 91109 (United States)
12. Universidad de Concepciòn, Departamento de Astronomía, Casilla 160-C, Concepciòn (Chile)

We present the first direct measurements of the rest-frame 10–40 keV X-ray luminosity function (XLF) of active galactic nuclei (AGNs) based on a sample of 94 sources at 0.1 < z < 3, selected at 8–24 keV energies from sources in the Nuclear Spectroscopic Telescope Array (NuSTAR) extragalactic survey program. Our results are consistent with the strong evolution of the AGN population seen in prior, lower-energy studies of the XLF. However, different models of the intrinsic distribution of absorption, which are used to correct for selection biases, give significantly different predictions for the total number of sources in our sample, leading to small, systematic differences in our binned estimates of the XLF. Adopting a model with a lower intrinsic fraction of Compton-thick sources and a larger population of sources with column densities N{sub H}∼10{sup 23−24} cm{sup −2} or a model with stronger Compton reflection component (with a relative normalization of R ∼ 2 at all luminosities) can bring extrapolations of the XLF from 2–10 keV into agreement with our NuSTAR sample. Ultimately, X-ray spectral analysis of the NuSTAR sources is required to break this degeneracy between the distribution of absorbing column densities and the strength of the Compton reflection component and thus refine our measurements of the XLF. Furthermore, the models that successfully describe the high-redshift population seen by NuSTAR tend to over-predict previous, high-energy measurements of the local XLF, indicating that there is evolution of the AGN population that is not fully captured by the current models.

• OSTI ID: 22882337
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 815; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
DISTRIBUTION
FORECASTING
GALACTIC EVOLUTION
GALAXY NUCLEI
KEV RANGE 01-10
LUMINOSITY
RED SHIFT
REFLECTION
TELESCOPES
X-RAY GALAXIES