THE DISCOVERY OF H_2O MASER EMISSION IN SEVEN ACTIVE GALACTIC NUCLEI AND AT HIGH VELOCITIES IN THE CIRCINUS GALAXY

摘要

We report the discovery of H_2O maser emission at 1.35 cm wavelength in seven active galactic nuclei (at distances of up to 80 Mpc) during a survey conducted at the 70 m diameter antenna of the NASA Deep Space Network near Canberra, Australia. The detection rate was ～4%. Two of the maser sources are particularly interesting because they display satellite high-velocity emission lines, which are a signature of emission from the accretion disks of supermassive black holes when seen edge-on. Three of the masers are coincident, to within uncertainties of 0″.2, with continuum emission sources that we observed at about λ = 1.3 cm. We also report the discovery of new spectral features in the Circinus galaxy H_2O maser that broaden the known velocity range of emission therein by a factor of ～1.7. If the new spectral features originate in the Circinus accretion disk, then molecular material must survive at radii ～3 times smaller than had been believed previously (～0.03 pc or ～2 x 10~5 Schwarzschild radii).