Extragalactic H2O Megamaser Sources: Central Black Holes, Nuclear X-ray and Maser Emissions ∗

Abstract

Extragalactic H2O megamasers are typically found within the innermost few parsecs of active galaxy nuclei (AGN) and the maser emission is considered to be excited most likely by the X-ray irradiation of the AGN. We investigate a comprehensive sample of extragalactic H2O masers in a sample of 38 maser host AGN to check potential correlations of the megamaser emission with parameters of the AGN, such as X-ray luminosity and black hole (BH) masses. We find a relation between the maser luminosities and BH masses, LH2O∝MBH3.6±0.4, which supports basically the theoretical prediction. The relation between the maser emission and X-ray emission is also confirmed.