NuSTAR observations of water megamaser AGN

Journal Article · Wed Apr 13 00:00:00 EDT 2016 · Astronomy and Astrophysics

DOI:https://doi.org/10.1051/0004-6361/201527689· OSTI ID:1313957

Masini, A.; Comastri, 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.

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.

• Research Organization: SLAC National Accelerator Lab., Menlo Park, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC); National Aeronautics and Space Administration (NASA)
• DOE Contract Number: AC02-76SF00515
• OSTI ID: 1313957
• Report Number(s): SLAC-PUB-16785; arXiv:1602.03185
• Journal Information: Astronomy and Astrophysics, Vol. 589; ISSN 0004-6361
• Publisher: EDP Sciences
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
masers
galaxies:active
galaxies: Seyfert