Compton-thick AGNs in the NuSTAR Era. III. A Systematic Study of the Torus Covering Factor

We present the analysis of a sample of 35 candidate Compton-thick active galactic nuclei (AGNs) selected in the nearby universe (average redshift ) with the Swift-BAT 100-month survey. All sources have available NuSTAR data, thus allowing us to constrain with unprecedented quality important spectral...

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Bibliographic Details
Published in:The Astrophysical journal 2019-02, Vol.872 (1), p.8
Main Authors: Marchesi, S., Ajello, M., Zhao, X., Marcotulli, L., Balokovi, M., Brightman, M., Comastri, A., Cusumano, G., Lanzuisi, G., La Parola, V., Segreto, A., Vignali, C.
Format: Article
Language:English
Subjects:
Active galactic nuclei
Astrophysics
Density
galaxies: active
galaxies: nuclei
Luminosity
Red shift
Toruses
X-rays: galaxies
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Summary:We present the analysis of a sample of 35 candidate Compton-thick active galactic nuclei (AGNs) selected in the nearby universe (average redshift ) 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 (NH,z), the average torus column density (NH,tor), and the torus covering factor (fc). We compare the best-fit results obtained with the widely used MYTorus (Murphy & Yaqoob 2009) model with those of the recently published borus02 model (Balokovi et al. 2018) used in the same geometrical configuration of MYTorus (i.e., with fc = 0.5). We find a remarkable agreement between the two, although with increasing dispersion in NH,z moving toward higher column densities. We then use borus02 to measure fc. High-fc sources have, on average, smaller offset between NH,z and NH,tor than low-fc ones. Therefore, low fc values can be linked to a "patchy torus" scenario, where the AGN is seen through an overdense region in the torus, while high-fc objects are more likely to be obscured by a more uniform gas distribution. Finally, we find potential evidence of an inverse trend between fc and the AGN 2-10 keV luminosity, i.e., sources with higher fc values have on average lower luminosities.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/aafbeb