A search for H 2O maser emission in nearby low-luminosity QSO host galaxies

Abstract

A sample of nearby galaxies hosting low-luminosity type 1 quasi-stellar objects (QSOs), previously studied in CO and Hi 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 H 2O 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 27-60mJy at spectral resolutions of ∼0.43kms -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°. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.