Water megamaser and central black hole masses in a large sample of galaxies

A. Farhan, E. N. Ercan, F. Tombesi

Published 2022-03-29Version 1

Extragalactic water megamaser emissions at 22 GHz have been playing vital roles in astrophysics. The limited detection rate of these masers has been motivating researchers to find clues that can help characterize them. The physical environments masers formed in is still ambiguous, accordingly, statistical studies have been thoroughly used to resolve these favorable environments. In this work, we go through the most essential parameter of Active Galactic Nuclei (AGN), namely, the mass of the central supermassive black hole (MBH) of the maser host galaxy. We study the correlation between maser luminosity (LH2O) and MBH. The regression line of the relation is also calculated. Additionally, sub-samples of megamasers (MMs), kilomasers (KMs), and disc masers are studied. Our results show a very significant LH2O-MBH correlation for our 68 galaxy sample. Unlike the results of previous works, dividing the sample into MMs and KMs gives no privilege to MM galaxies. In opposite to expectation, KMs have weak and low significant LH2O - MBH correlation, while MMs show no correlation. The positive correlation in KMs can be explained by the role of AGN therein, while the diversity of MMs types, with some of which are not strongly related to AGN, may explain the correlation missing. The 28 disc maser sample, where tight correlation is expected, surprisingly shows a very weak and low significant LH2O - MBH correlation. Future VLBI studies will eventually lead to a certain classification of a good number of maser galaxies, which is essential to clearly establish the LH2O-MBH relation.