The NuSTAR Local AGN N <sub>H</sub> Distribution Survey (NuLANDS). I. Toward a Truly Representative Column Density Distribution in the Local Universe

Abstract Hard X-ray-selected samples of active galactic nuclei (AGN) provide one of the cleanest views of supermassive black hole accretion but are biased against objects obscured by Compton-thick gas column densities of N H &gt; 10 24 cm −2 . To tackle this issue, we present the NuSTAR Local AGN N H Distribution Survey (NuLANDS)—a legacy sample of 122 nearby ( z &lt; 0.044) AGN primarily selected to have warm infrared colors from IRAS between 25 and 60 μ m. We show that optically classified Type 1 and 2 AGN in NuLANDS are indistinguishable in terms of optical [O iii ] line flux and mid-to-far-infrared AGN continuum bolometric indicators, as expected from an isotropically selected AGN sample, while Type 2 AGN are deficient in terms of their observed hard X-ray flux. By testing many X-ray spectroscopic models, we show the measured line-of-sight column density varies on average by ∼1.4 orders of magnitude depending on the obscurer geometry. To circumvent such issues, we propagate the uncertainties per source into the parent column density distribution, finding a directly measured Compton-thick fraction of 35% ± 9%. By construction, our sample will miss sources affected by severe narrow-line reddening, and thus segregates sources dominated by small-scale nuclear obscuration from large-scale host-galaxy obscuration. This bias implies an even higher intrinsic obscured AGN fraction may be possible, although tests for additional biases arising from our infrared selection find no strong effects on the measured column density distribution. NuLANDS thus holds potential as an optimized sample for future follow-up with current and next-generation instruments aiming to study the local AGN population in an isotropic manner.

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Publication Details

Journal
The Astrophysical Journal
Published
2024-12-30
DOI
https://doi.org/10.3847/1538-4357/ad8236
Citations
11
Primary Topic
Astrophysical Phenomena and Observations
Type
article
Field-Weighted Citation Impact
3.65

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article

The NuSTAR Local AGN N H Distribution Survey (NuLANDS). I. Toward a Truly Representative Column Density Distribution in the Local Universe

Jiří Svoboda, Murray Brightman, B. Mingo, Ezequiel Treister et al.
11 citations
The Astrophysical Journal
Astrophysical Phenomena and Observations
3.65
article

The NuSTAR Local AGN N H Distribution Survey (NuLANDS). I. Toward a Truly Representative Column Density Distribution in the Local Universe

Jiří Svoboda, Murray Brightman, B. Mingo, Ezequiel Treister, S. Hoenig, W. N. Brandt, F. Civano, Kristin K. Madsen, G. B. Lansbury, Cláudio Ricci, Chien‐Ting Chen, Lauranne Lanz, D. Asmus, Stefano Marchesi, Michael Koss, F. E. Bauer, Daniel Stern, Karl Förster, Stephanie LaMassa, M. L. Parker, Matthew Middleton, A. Annuar, D. Farrah, Elias Kammoun, Yoshihiro Ueda, Brian W. Grefenstette, Peter Boorman, Claire Greenwell, C. M. Urry, Johannes Büchner, A. B. Hill, P. Gandhi, Fiona Harrison, L. Zappacosta, D. M. Alexander, Mislav Baloković
article en
11 citations

Abstract

Abstract Hard X-ray-selected samples of active galactic nuclei (AGN) provide one of the cleanest views of supermassive black hole accretion but are biased against objects obscured by Compton-thick gas column densities of N H &gt; 10 24 cm −2 . To tackle this issue, we present the NuSTAR Local AGN N H Distribution Survey (NuLANDS)—a legacy sample of 122 nearby ( z &lt; 0.044) AGN primarily selected to have warm infrared colors from IRAS between 25 and 60 μ m. We show that optically classified Type 1 and 2 AGN in NuLANDS are indistinguishable in terms of optical [O iii ] line flux and mid-to-far-infrared AGN continuum bolometric indicators, as expected from an isotropically selected AGN sample, while Type 2 AGN are deficient in terms of their observed hard X-ray flux. By testing many X-ray spectroscopic models, we show the measured line-of-sight column density varies on average by ∼1.4 orders of magnitude depending on the obscurer geometry. To circumvent such issues, we propagate the uncertainties per source into the parent column density distribution, finding a directly measured Compton-thick fraction of 35% ± 9%. By construction, our sample will miss sources affected by severe narrow-line reddening, and thus segregates sources dominated by small-scale nuclear obscuration from large-scale host-galaxy obscuration. This bias implies an even higher intrinsic obscured AGN fraction may be possible, although tests for additional biases arising from our infrared selection find no strong effects on the measured column density distribution. NuLANDS thus holds potential as an optimized sample for future follow-up with current and next-generation instruments aiming to study the local AGN population in an isotropic manner.

The Astrophysical JournalVol. 978(1)
Smithsonian Institution, National Aeronautics and Space Administration, John Templeton Foundation, California Institute of Technology, Harvard University, Royal Astronomical Society, UK-India Education and Research Initiative, University of Leicester, National Research Foundation, University Grants Commission, Grantová Agentura České Republiky, Nuclear Safety and Security Commission, Universiti Kebangsaan Malaysia, Agencia Nacional de Investigación y Desarrollo, Jet Propulsion Laboratory, Goddard Space Flight Center, University of California, Los Angeles, Smithsonian Astrophysical Observatory, Science and Technology Facilities Council, Astrophysics Science Division, Astrophysics Division
Openalex Percentile: Top 7%
Astrophysical Phenomena and Observations
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