Water megamaser emission in hard X-ray selected AGN

摘要: Water megamaser emission at 22 GHz has proven to be a powerful tool for astrophysical studies of AGN allowing an accurate determination the central black hole mass and accretion disc geometry dynamics. However, after searches among thousands galaxies, only ~ 200 them have shown such spectroscopic features, most uncertain classification. In addition, physical geometrical conditions under which maser activates are still unknown. this work we aim characterizing occurrence water in unbiased sample AGN, investigating relation with X-ray properties possible favorable needed detect maser. We searched hard selected taken from INTEGRAL/IBIS survey above 20 keV. Of 380 sources sample, half data. also considered sub-sample 87 sources, volume limited, obtained new Green Bank Telescope Effelsberg observations (for 35 sources), detecting one increasing its radio coverage 75%. The detection rate total is 15+/-3%, fraction raises up 19+/-5% complete sub-sample, especially if considering type 2 Compton thick AGN. These results demonstrate that selection may significantly enhance efficiency over comparably large optical/infrared surveys. A decline luminosity might suggest extreme luminous nuclear environment does not favour emission. CT could explained terms effects, being medium very edge-on portion obscuring medium.