Discovery of Water Maser Emission in Eight AGNs with 70 m Antennas of NASA’s Deep Space Network

We report the discovery of water maser emission in eight active galacticnuclei (AGN) with the 70-m NASA Deep Space Network (DSN) antennas atTidbinbilla, Australia and Robledo, Spain. The positions of the newlydiscovered masers, measured with the VLA, are consistent with the opticalpositions of the host nuclei to within 1 sigma (0.3 arcsec radio and 1.3 arcsecoptical) and most likely mark the locations of the embedded central engines.The spectra of two sources, NGC 3393 and NGC 5495, display the characteristicspectral signature of emission from an edge-on accretion disk, with orbitalvelocities of ~600 and ~400 km s^-1, respectively. In a survey with DSNfacilities of 630 AGN selected from the NASA Extragalactic Database, we havediscovered a total of 15 water maser sources. The resulting incidence rate ofmaser emission among nearby (v_sys < 7000 km s^-1) Seyfert 1.8-2.0 and LINERsystems is ~10 percent for a typical rms noise level of ~14 mJy over 1.3 kms^-1 spectral channels. As a result of this work, the number of nearby AGN(v_sys < 7000 km s^-1) observed with <20 mJy rms noise has increased from 130to 449.Comment: 7 pages, 1 figure, 2 tables, to appear in the 2006 February 10 issue of the Astrophysical Journal, uses twocolumns.cl