The N_H Distribution of Hard X-Ray Selected Active Galactic Nuclei in the NEP Field
Creators
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1.
University of Utah
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Goddard Space Flight Center
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University of Illinois Urbana-Champaign
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California Institute of Technology
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Arizona State University
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Wayne State University
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Space Telescope Science Institute
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University of Arizona
Abstract
X-ray surveys are one of the most unbiased methods for detecting Compton-thick (CT; NH ≥ 1024 cm−2) active galactic nuclei (AGN), which are thought to comprise up to 60% of AGN within z ≲ 1.0. These CT AGN are often difficult to detect with current instruments, but the X-ray data within the JWST-North Ecliptic Pole (NEP) Time Domain Field present a unique opportunity to study faint and obscured AGN. The NEP contains the deepest NuSTAR survey to date, and X. Zhao et al. detected 60 hard X-ray sources from the combined exposure of NuSTAR’s Cycle 5 and 6 observations. In this work, we utilize the NuSTAR Cycle 5+6+8+9 data and simultaneous XMM-Newton observations in order to perform the first spectroscopic analysis of the 60 source catalog. We present this analysis and measure the NH distribution of the sample. We measure an observed CT fraction of 0.13_(−0.04)^(+0.15) down to an observed 8–24 keV flux of 6.0 × 10−14 erg s cm−2, and we correct our analysis for absorption bias to estimate an underlying CT fraction of 0.32_(−0.08)^(+0.23). The derived obscuration distribution and CT fraction are consistent with population synthesis models and previous surveys.
Copyright and License
© 2025. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Acknowledgement
The material is based upon work supported by NASA under award Nos. 80GSFC21M0002 and 80NSSC24K1482. This work made use of data from the NuSTAR mission, which is led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. Additionally, this work made use of data from XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. C.N.A.W. acknowledges funding from JWST/NIRCam contract No. NAS5-02015 to the University of Arizona.
This research used data obtained with the Dark Energy Spectroscopic Instrument (DESI). DESI construction and operations are managed by the Lawrence Berkeley National Laboratory. This material is based upon work supported by the US Department of Energy (DOE), Office of Science, Office of High-Energy Physics, under contract No. DE-AC02-05CH11231, and by the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility under the same contract. Additional support for DESI was provided by the US National Science Foundation (NSF), Division of Astronomical Sciences under contract No. AST-0950945 to the NSF’s National Optical-Infrared Astronomy Research Laboratory; the Science and Technology Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the French Alternative Energies and Atomic Energy Commission (CEA); the National Council of Humanities, Science and Technology of Mexico (CONAHCYT); the Ministry of Science and Innovation of Spain (MICINN), and by the DESI Member Institutions: www.deswww.desi.lbl.gov/collaborating-institutions. The DESI Collaboration is honored to be permitted to conduct scientific research on I’oligam Du’ag (Kitt Peak), a mountain with particular significance to the Tohono O’odham Nation. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the US NSF, the US DOE, or any of the listed funding agencies.
This work also made extensive use of Astropy (Astropy Collaboration et al. 2013, 2018, 2022), numpy (C. R. Harris et al. 2020), and SciPy (P. Virtanen et al. 2020). We would also like to thank the High Energy Astrophysics Science Archive Research Center (HEASARC) team; this work would not have been possible without their data and software.
We thank the anonymous referee for their comments, which greatly improved this paper. Lastly, we thank Steven Willner for his comments and Luca Zappacosta for the helpful discussion.
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Additional details
Additional titles
- Alternative title
- The N_H Distribution of Hard X-ray Selected AGN in the NEP Field
Related works
- Is new version of
- Discussion Paper: arXiv:2510.26554 (arXiv)
Funding
- National Aeronautics and Space Administration
- 80GSFC21M0002
- National Aeronautics and Space Administration
- 80NSSC24K1482
- National Aeronautics and Space Administration
- NAS5-02015
- United States Department of Energy
- DE-AC02-05CH11231
- National Science Foundation
- AST-0950945
Dates
- Submitted
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2025-06-11
- Accepted
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2025-10-28
- Available
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2025-12-17Published