The NuSTAR Serendipitous Survey: The 40 month Catalog and the Properties of the Distant High Energy X-ray Source Population

• Published in: arXiv.org 2016-12
• Main Authors: Lansbury, G B, Stern, D, Aird, J, Alexander, D M, Fuentes, C, Harrison, F A, Treister, E, Bauer, F E, Tomsick, J A, Balokovic, M, A Del Moro, Gandhi, P, Ajello, M, Annuar, A, Ballantyne, D R, Boggs, S E, Brandt, N, Brightman, M, Chen, C J, Christensen, F E, Civano, F, Comastri, A, Craig, W W, ster, K, Grefenstette, B W, Hailey, C J, Hickox, R, Jiang, B, Jun, H, Koss, M, Marchesi, S, Melo, A D, Mullaney, J R, Noirot, G, Schulze, S, Walton, D J, Zappacosta, L, Zhang, W
• Format: Article
• Language: English
• Subjects: Active galactic nuclei; Infrared analysis; Luminosity; Missions; Optical properties; Red shift; Sky surveys (astronomy); X ray sources; XMM (spacecraft)
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1612.06389

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 = 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 ( 10^44 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