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

Marchesi, S. and Ajello, M. and Zhao, X. and Marcotulli, L. and Baloković, M. and Brightman, M. and Comastri, A. and Cusumano, G. and Lanzuisi, G. and La Parola, V. and Segreto, A. and Vignali, C. (2019) Compton-thick AGNs in the NuSTAR Era. III. A Systematic Study of the Torus Covering Factor. Astrophysical Journal, 872 (1). Art. No. 8. ISSN 1538-4357. doi:10.3847/1538-4357/aafbeb.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Marchesi, S.0000-0001-5544-0749
Ajello, M.0000-0002-6584-1703
Baloković, M.0000-0003-0476-6647
Brightman, M.0000-0002-8147-2602
Comastri, A.0000-0003-3451-9970
Lanzuisi, G.0000-0001-9094-0984
La Parola, V.0000-0002-8087-6488
Vignali, C.0000-0002-8853-9611
Additional Information:© 2019 The American Astronomical Society. Received 2018 July 15; revised 2018 November 23; accepted 2018 December 20; published 2019 February 6. We thank an anonymous referee for the useful comments, which helped in improving the paper. S.M., M.A., and X.Z. acknowledge funding under NASA contract 80NSSC17K0635. Mi.Ba. acknowledges support from the Black Hole Initiative at Harvard University, which is funded by a grant from the John Templeton Foundation. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester, as well as of the TOPCAT software (Taylor 2005) for the analysis of data tables.
Group:NuSTAR, Space Radiation Laboratory
Funding AgencyGrant Number
Harvard UniversityUNSPECIFIED
John Templeton FoundationUNSPECIFIED
Subject Keywords:galaxies: active – galaxies: nuclei – X-rays: galaxies
Issue or Number:1
Record Number:CaltechAUTHORS:20190206-100219625
Persistent URL:
Official Citation:S. Marchesi et al 2019 ApJ 872 8
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92711
Deposited By: Tony Diaz
Deposited On:06 Feb 2019 18:11
Last Modified:16 Nov 2021 03:52

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