Lansbury, GB;
Alexander, DM;
Aird, J;
Gandhi, P;
Stern, D;
Koss, M;
Lamperti, I;
... Zappacosta, L; + view all
(2017)
The NuSTAR Serendipitous Survey: Hunting for the Most Extreme Obscured AGN at >10 keV.
The Astrophysical Journal
, 846
(1)
, Article 20. 10.3847/1538-4357/aa8176.
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Abstract
We identify sources with extremely hard X-ray spectra (i.e., with photon indices of G 0.6) in the 13 deg2 NuSTAR serendipitous survey, to search for the most highly obscured active galactic nuclei (AGNs) detected at >10 keV. Eight extreme NuSTAR sources are identified, and we use the NuSTAR data in combination with lower-energy X-ray observations (from Chandra, Swift XRT, and XMM-Newton) to characterize the broadband (0.5–24 keV) X-ray spectra. We find that all of the extreme sources are highly obscured AGNs, including three robust Compton-thick (CT; NH > ´ 1.5 1024 cm−2 ) AGNs at low redshift (z < 0.1) and a likely CT AGN at higher redshift (z = 0.16). Most of the extreme sources would not have been identified as highly obscured based on the low-energy (<10 keV) X-ray coverage alone. The multiwavelength properties (e.g., optical spectra and X-ray–mid-IR luminosity ratios) provide further support for the eight sources being significantly obscured. Correcting for absorption, the intrinsic rest-frame 10–40 keV luminosities of the extreme sources cover a broad range, from » ´5 1042 to 1045 erg s−1 . The estimated number counts of CT AGNs in the NuSTAR serendipitous survey are in broad agreement with model expectations based on previous X-ray surveys, except for the lowest redshifts (z < 0.07), where we measure a high CT fraction of = - + f CT obs 30 %12 16 . For the small sample of CT AGNs, we find a high fraction of galaxy major mergers (50% ± 33%) compared to control samples of “normal” AGNs.
| Type: | Article |
|---|---|
| Title: | The NuSTAR Serendipitous Survey: Hunting for the Most Extreme Obscured AGN at >10 keV |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.3847/1538-4357/aa8176 |
| Publisher version: | https://doi.org/10.3847/1538-4357/aa8176 |
| Language: | English |
| Additional information: | This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | galaxies: active; galaxies: nuclei; quasars: general; surveys; X-rays: galaxies |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10091818 |
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