NuSTAR observations of heavily obscured quasars at z ∼ 0.5

Journal Article · Thu Apr 10 04:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/785/1/17· OSTI ID:22357186

Lansbury, G. B.; Alexander, D. M.; Moro, A. Del; Gandhi, P.; Aird, J. ^[1]; Assef, R. J. ^[2]; Stern, D. ^[3]; Ballantyne, D. R. ^[4]; Baloković, M.; Grefenstette, B. W.; Harrison, F. A. ^[5]; Bauer, F. E. ^[6]; Boggs, S. E. ^[7]; Brandt, W. N. ^[8]; Christensen, F. E.; Craig, W. W. ^[9]; Elvis, M. ^[10]; Hailey, C. J. ^[11]; Hickox, R. C. ^[12]; others, and

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1. Department of Physics, University of Durham, South Road, Durham DH1 3LE (United Kingdom)
2. Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago (Chile)
3. Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 169-221, Pasadena, CA 91109 (United States)
4. Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States)
5. Cahill Center for Astrophysics, 1216 East California Boulevard, California Institute of Technology, Pasadena, CA 91125 (United States)
6. Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Catlica de Chile, Casilla 306, Santiago 22 (Chile)
7. Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)
8. Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States)
9. DTU Space-National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark)
10. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
11. Columbia Astrophysics Laboratory, 550 W 120th Street, Columbia University, NY 10027 (United States)
12. Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States)

We present NuSTAR hard X-ray observations of three Type 2 quasars at z ≈ 0.4-0.5, optically selected from the Sloan Digital Sky Survey. Although the quasars show evidence for being heavily obscured, Compton-thick systems on the basis of the 2-10 keV to [O III] luminosity ratio and multiwavelength diagnostics, their X-ray absorbing column densities (N {sub H}) are poorly known. In this analysis, (1) we study X-ray emission at >10 keV, where X-rays from the central black hole are relatively unabsorbed, in order to better constrain N {sub H}. (2) We further characterize the physical properties of the sources through broad-band near-UV to mid-IR spectral energy distribution analyses. One of the quasars is detected with NuSTAR at >8 keV with a no-source probability of <0.1%, and its X-ray band ratio suggests near Compton-thick absorption with N {sub H} ≳ 5 × 10{sup 23} cm{sup –2}. The other two quasars are undetected, and have low X-ray to mid-IR luminosity ratios in both the low-energy (2-10 keV) and high-energy (10-40 keV) X-ray regimes that are consistent with extreme, Compton-thick absorption (N {sub H} ≳ 10{sup 24} cm{sup –2}). We find that for quasars at z ∼ 0.5, NuSTAR provides a significant improvement compared to lower energy (<10 keV) Chandra and XMM-Newton observations alone, as higher column densities can now be directly constrained.

• OSTI ID: 22357186
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 785; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BLACK HOLES
COMPARATIVE EVALUATIONS
DENSITY
EMISSION
ENERGY SPECTRA
HARD X RADIATION
KEV RANGE
LUMINOSITY
QUASARS
X-RAY GALAXIES