A search for H2O maser emission in nearby low-luminosity QSO host galaxies

A sample of nearby galaxies hosting low-luminosity type 1 quasi-stellar objects (QSOs), previously studied in CO and H i emission lines, has been searched for maser emission. Using the Effelsberg 100-m telescope, we observed 17 sources with redshifts of z≤ 0.06 and δ > −30° for emission in the 22-GHz water vapour maser transition. The sample objects have been drawn from a wide-angle survey for optically bright QSOs (Hamburg/ESO survey, HES). No host galaxies from the sample have been detected in the water maser emission line. In this paper we review the discussion on the reasons for H2O megamasers being rarely found in Seyfert 1 galaxies. Eight of them are bulge dominated and probably of elliptical type (E/S0), whereas six have spiral geometry. Three of the objects seem to be in a phase of merging/interaction. We found 3σ upper limits for the flux density of 27–60 mJy at spectral resolutions of ∼0.43 km s^-1. We furthermore find that the viewing angle to the line of sight to the galaxy, under which the probability to detect megamaser emission is the highest, is about 6°.