On the Accretion Rates of Host AGN of H₂O Masers

Extragalactic H₂O megamasers (L_maser >10 L_⊙)are typically found within the innermost regions of a few parsecs of galaxy centers and the Active Galactic Nuclei (AGN)are considered to be their ultimate energy sources. The host AGN of H₂O masers may have some intrinsic properties not present in AGN without detected maser emission. For the purpose of finding these unique properties, we investigate all published nuclear maser sources and assemble a sample of 39 such sources with available observed X-ray data. Their dimensionless accretion rates (logL_2-10keV/L_Edd with L_2-10keV and L_Edd for the intrinsic 2-10keV X-ray luminosities and Eddington luminosities, respectively)are derived based on their X-ray data and our estimated mass values of the nuclear engines. We compare the results to the dimensionless accretion rates of a complete non-maser AGN sample at similar distances.The comparison shows that host AGN of H₂O masers tend to have higher dimensionless accretion rates.We also calculate the mass accretion rates for both samples. A similar trend appears, i.e., AGN with masers have higher accretion rates, which needs to be checked with a future larger sample. We further investigate possible connections between the accretion rates (both mass and dimensionless accretion rates)and H₂O maser emission luminosities. We do not find any significant correlation between accretion rates and isotropic maser luminosities.