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The NuSTAR serendipitous survey : the 40-month catalog and the properties of the distant high-energy X-ray source population.

Lansbury, G. B. and Stern, D. and Aird, J. and Alexander, D. M. and Fuentes, C. and Harrison, F. A. and Treister, E. and Bauer, F. E. and Tomsick, J. A. and Balokovic, M. and Del Moro, A. and Gandhi, P. and Ajello, M. and Annuar, A. and Ballantyne, D. R. and Boggs, S. E. and Brandt, N. and Brightman, M. and Chen, C. J. and Christensen, F. E. and Civano, F. and Comastri, A. and Craig, W. W. and Forster, K. and Grefenstette, B. W. and Hailey, C. J. and Hickox, R. and Jiang, B. and Jun, H. and Koss, M. and Marchesi, S. and Melo, A. D. and Mullaney, J. R. and Noirot, G. and Schulze, S. and Walton, D. J. and Zappacosta, L. and Zhang, W. (2017) 'The NuSTAR serendipitous survey : the 40-month catalog and the properties of the distant high-energy X-ray source population.', Astrophysical journal., 836 (1). p. 99.


We present the first full catalog and science results for the NuSTAR serendipitous survey. The catalog incorporates data taken during the first 40 months of NuSTAR operation, which provide ~20Ms of effective exposure time over 331 fields, with an areal coverage of 13 sq deg, and 497 sources detected in total over the 3-24 keV energy range. There are 276 sources with spectroscopic redshifts and classifications, largely resulting from our extensive campaign of ground-based spectroscopic followup. We characterize the overall sample in terms of the X-ray, optical, and infrared source properties. The sample is primarily comprised of active galactic nuclei (AGNs), detected over a large range in redshift from z = 0.002 - 3.4 (median of <z> = 0.56), but also includes 16 spectroscopically confirmed Galactic sources. There is a large range in X-ray flux, from log( f_3-24keV / erg s^-1 cm^-2 ) ~ -14 to -11, and in rest-frame 10-40 keV luminosity, from log( L_10-40keV / erg s^-1 ) ~ 39 to 46, with a median of 44.1. Approximately 79% of the NuSTAR sources have lower energy (<10 keV) X-ray counterparts from XMM-Newton, Chandra, and Swift/XRT. The mid-infrared (MIR) analysis, using WISE all-sky survey data, shows that MIR AGN color selections miss a large fraction of the NuSTAR-selected AGN population, from ~15% at the highest luminosities (Lx > 10^44 erg s^-1) to ~80% at the lowest luminosities (Lx < 10^43 erg s^-1). Our optical spectroscopic analysis finds that the observed fraction of optically obscured AGNs (i.e., the Type 2 fraction) is F_Type2 = 53(+14-15)%, for a well-defined subset of the 8-24 keV selected sample. This is higher, albeit at a low significance level, than the Type 2 fraction measured for redshift- and luminosity-matched AGNs selected by <10 keV X-ray missions.

Item Type:Article
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Publisher statement:© 2017. The American Astronomical Society. All rights reserved.
Date accepted:07 December 2016
Date deposited:07 February 2017
Date of first online publication:10 February 2017
Date first made open access:No date available

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