NuSTAR observations of water megamaser AGN
Journal
Date Issued
2016
Author(s)
Masini, A.
•
•
Baloković, M.
•
Zaw, I.
•
Puccetti, S.
•
Ballantyne, D. R.
•
Bauer, F. E.
•
Boggs, S. E.
•
Brandt, W. N.
•
Brightman, M.
•
Christensen, F. E.
•
Craig, W. W.
•
Gandhi, P.
•
Hailey, C. J.
•
Harrison, F. A.
•
Koss, M. J.
•
Madejski, G.
•
Ricci, C.
•
Rivers, E.
•
Stern, D.
•
Zhang, W. W.
Abstract
Aims: We study the connection between the masing disk and obscuring torus in Seyfert 2 galaxies. Methods: We present a uniform X-ray spectral analysis of the high energy properties of 14 nearby megamaser active galactic nuclei observed by NuSTAR. We use a simple analytical model to localize the maser disk and understand its connection with the torus by combining NuSTAR spectral parameters with the available physical quantities from VLBI mapping. Results: Most of the sources that we analyzed are heavily obscured, showing a column density in excess of ~1023 cm-2; in particular, 79% are Compton-thick (NH > 1.5 × 1024 cm-2). When using column densities measured by NuSTAR with the assumption that the torus is the extension of the maser disk, and further assuming a reasonable density profile, we can predict the torus dimensions. They are found to be consistent with mid-IR interferometry parsec-scale observations of Circinus and NGC 1068. In this picture, the maser disk is intimately connected to the inner part of the torus. It is probably made of a large number of molecular clouds that connect the torus and the outer part of the accretion disk, giving rise to a thin disk rotating in most cases in Keplerian or sub-Keplerian motion. This toy model explains the established close connection between water megamaser emission and nuclear obscuration as a geometric effect.
Volume
589
Start page
A59
Issn Identifier
0004-6361
Ads BibCode
2016A&A...589A..59M
Rights
open.access
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