2013MNRAS.436.3388C

Large column densities, derived from X-ray studies, are typically measured towards active galactic nuclei (AGN) hosting water masers, especially when the H2O emission is associated with the nuclear accretion disc. In addition, possible correlations between the intrinsic X-ray luminosity and the characteristics of the H2O maser emission have been put forward that, however, require confirmation. We have performed high-sensitivity XMM-Newton observations of a sample of five H2O maser sources confidently detected in our ongoing survey with the Swift satellite of all known water masers in AGN, in order to obtain detailed X-ray information of these promising targets and to set up a systematic detailed study of the X-ray/H2O maser relation in AGN. For three galaxies, NGC 613, VII Zw 73 and IRAS 16288+3929, the amount of intrinsic absorption has been estimated, indicating column densities of 4-6x10²³/cm2. For UGC 3789 and NGC 6264 (the two confirmed disc-maser galaxies in our sample), column densities in excess of 1x10²⁴/cm2 are inferred from the large EW of the Fe Kα line. By adding our results to those obtained in past similar studies, we find that the percentage of water masers sources that host highly obscured (NH > 10²³/cm2) and Compton-thick AGN is 96 (45/47) and 57 percent (27/47), respectively. In addition, 86 percent, 18/21 of disc-maser galaxies host Compton-thick AGN. The correlation between the galaxies' bolometric luminosity and accretion disc radius, suggested in previous works, is also confirmed.