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NuSTAR unveils a compton-thick type 2 quasar in Mrk 34.

Gandhi, P. and Lansbury, G.B. and Alexander, D.M. and Stern, D. and Arévalo, P. and Ballantyne, D.R. and Baloković, M. and Bauer, F.E. and Boggs, S.E. and Brandt, W.N. and Brightman, M. and Christensen, F.E. and Comastri, A. and Craig, W.W. and Del Moro, A. and Elvis, M. and Fabian, A.C. and Hailey, C.J. and Harrison, F.A. and Hickox, R.C. and Koss, M. and LaMassa, S.M. and Luo, B. and Madejski, G.M. and Ptak, A.F. and Puccetti, S. and Teng, S.H. and Urry, C.M. and Walton, D.J. and Zhang, W.W. (2014) 'NuSTAR unveils a compton-thick type 2 quasar in Mrk 34.', Astrophysical journal., 792 (2). p. 117.


We present Nuclear Spectroscopic Telescope Array (NuSTAR) 3-40 keV observations of the optically selected Type 2 quasar (QSO2) SDSS J1034+6001 or Mrk 34. The high-quality hard X-ray spectrum and archival XMM-Newton data can be fitted self-consistently with a reflection-dominated continuum and a strong Fe Kα fluorescence line with equivalent width >1 keV. Prior X-ray spectral fitting below 10 keV showed the source to be consistent with being obscured by Compton-thin column densities of gas along the line of sight, despite evidence for much higher columns from multiwavelength data. NuSTAR now enables a direct measurement of this column and shows that N H lies in the Compton-thick (CT) regime. The new data also show a high intrinsic 2-10 keV luminosity of L 2-10 ~ 1044 erg s–1, in contrast to previous low-energy X-ray measurements where L 2-10 lsim 1043 erg s–1 (i.e., X-ray selection below 10 keV does not pick up this source as an intrinsically luminous obscured quasar). Both the obscuring column and the intrinsic power are about an order of magnitude (or more) larger than inferred from pre-NuSTAR X-ray spectral fitting. Mrk 34 is thus a "gold standard" CT QSO2 and is the nearest non-merging system in this class, in contrast to the other local CT quasar NGC 6240, which is currently undergoing a major merger coupled with strong star formation. For typical X-ray bolometric correction factors, the accretion luminosity of Mrk 34 is high enough to potentially power the total infrared luminosity. X-ray spectral fitting also shows that thermal emission related to star formation is unlikely to drive the observed bright soft component below ~3 keV, favoring photoionization instead.

Item Type:Article
Additional Information:
Keywords:Galaxies: active, X-rays: galaxies, X-rays: individual (Mrk 34)
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Publisher statement:© 2014. The American Astronomical Society. All rights reserved.
Date accepted:06 July 2014
Date deposited:21 May 2015
Date of first online publication:September 2014
Date first made open access:No date available

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