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|Title:||The properties of the AGN torus as revealed from a set of unbiased NuSTAR observations||Authors:||Zhao, X.
|Issue Date:||2021||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||650||First Page:||A57||Abstract:||The obscuration observed in active galactic nuclei (AGNs) is mainly caused by dust and gas distributed in a torus-like structure surrounding the supermassive black hole. However, the properties of the obscuring torus of an AGN in X-ray have not yet been fully investigated because of a lack of high-quality data and proper models. In this work, we perform a broadband X-ray spectral analysis of a large, unbiased sample of obscured AGNs (with line-of-sight column density 23 ≤ log(N<SUB>H</SUB>) ≤ 24) in the nearby Universe for which high-quality archival NuSTAR data are available. We analyzed the source spectra using the recently developed borus02 model, which enables us to accurately characterize the physical and geometrical properties of AGN-obscuring tori. We compare our results obtained from the unbiased Compton-thin AGNs with those of Compton-thick AGNs. We find that Compton-thin and Compton-thick AGNs may possess similar tori, whose average column density is Compton thick (N<SUB>H, tor, ave</SUB> ≈ 1.4 × 10<SUP>24</SUP> cm<SUP>−2</SUP>), but they are observed through different (under-dense or over-dense) regions of the tori. We also find that the obscuring torus medium is significantly inhomogeneous, with the torus average column densities being significantly different from their line-of-sight column densities (for most of the sources in the sample). The average torus covering factor of sources in our unbiased sample is c<SUB>f</SUB> = 0.67, suggesting that the fraction of unobscured AGNs is ∼33%. We developed a new method to measure the intrinsic line-of-sight column density distribution of AGNs in the nearby Universe, and find the results to be in good agreement with constraints from recent population synthesis models.||URI:||http://hdl.handle.net/20.500.12386/32213||URL:||https://www.aanda.org/articles/aa/full_html/2021/06/aa40297-21/aa40297-21.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/202140297||Bibcode ADS:||2021A&A...650A..57Z||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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