We present the analysis of a sample of 35 candidate Compton-thick active galactic nuclei (AGNs) selected in the nearby universe (average redshift ázñ 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 (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.

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

Marchesi S.
Writing – Original Draft Preparation
;
Lanzuisi G.
Membro del Collaboration Group
;
Vignali C.
Membro del Collaboration Group
2019

Abstract

We present the analysis of a sample of 35 candidate Compton-thick active galactic nuclei (AGNs) selected in the nearby universe (average redshift ázñ 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 (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.
2019
Marchesi S.; Ajello M.; Zhao X.; Marcotulli L.; Balokovic M.; Brightman M.; Comastri A.; Cusumano G.; Lanzuisi G.; La Parola V.; Segreto A.; Vignali C.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/741812
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