
TY  - JOUR
A1  - Maloney, Philip R. 
T1  - Powerful Water Masers in Active Galactic Nuclei
JF  - Publications of the Astronomical Society of Australia
JO  - Publ. Astron. Soc.  Aust.
Y1  - 2002
VL  - 19
IS  - 4
SP  - 401
EP  - 421
KW  - galaxies: Seyfert &#8212; masers &#8212; molecular lines &#8212; radio lines: galaxies &#8212; accretion, accretion disks
UR  - https://doi.org/10.1071/AS01100 
N2  - Luminous water maser emission in the 616&#8211;523 line at 22GHz has been detected from two dozen galaxies. In all cases the emission is confined to the nucleus and has been found only in AGN, in particular, in Type 2 Seyferts and LINERs. I argue that most of the observed megamaser sources are powered by X-ray irradiation of dense gas by the central engine. After briefly reviewing the physics of these X-Ray Dissociation Regions, I discuss in detail the observations of the maser disk in NGC 4258, its implications, and compare alternative models for the maser emission. I then discuss the observations of the other sources that have been imaged with VLBI to date, and how they do or do not fit into the framework of a thin, rotating disk, as in NGC 4258. Finally, I briefly discuss future prospects, especially the possibility of detecting other water maser transitions. 
ER  -

