Compton-thick AGNs in the NuSTAR Era. III. A Systematic Study of the Torus Covering Factor
Journal
Date Issued
2019
Author(s)
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Ajello, M.
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Zhao, X.
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Marcotulli, L.
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Baloković, M.
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Brightman, M.
•
•
•
•
•
•
Vignali, C.
Abstract
We present the analysis of a sample of 35 candidate Compton-thick active galactic nuclei (AGNs) selected in the nearby universe (average redshift < z> ∼ 0.03) with the Swift-BAT 100-month survey. All sources have available NuSTAR data, thus allowing us to constrain with unprecedented quality important spectral parameters such as the obscuring torus line-of-sight column density (N_H,z), the average torus column density (N_H,tor), and the torus covering factor (f_c ). We compare the best-fit results obtained with the widely used MYTorus (Murphy & Yaqoob 2009) model with those of the recently published borus02 model (Baloković et al. 2018) used in the same geometrical configuration of MYTorus (i.e., with f_c = 0.5). We find a remarkable agreement between the two, although with increasing dispersion in N_H,z moving toward higher column densities. We then use borus02 to measure f_c . High-f_c sources have, on average, smaller offset between N_H,z and N_H,tor than low-f_c ones. Therefore, low f_c values can be linked to a “patchy torus” scenario, where the AGN is seen through an overdense region in the torus, while high-f_c objects are more likely to be obscured by a more uniform gas distribution. Finally, we find potential evidence of an inverse trend between f_c and the AGN 2-10 keV luminosity, i.e., sources with higher f_c values have on average lower luminosities.
Volume
872
Issue
1
Start page
8
Issn Identifier
0004-637X
Ads BibCode
2019ApJ...872....8M
Rights
open.access
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