Henkel, Wang, Falcke et al./H2O masers in FR I radio galaxies

H2O megamaser emission from FR I radio galaxies

C. Henkel(1,2), Y.P. Wang(1,3), H. Falcke(1,4), A.S. Wilson(4,5), J.A. Braatz(6)

(1)Max-Planck-Institut für Radioastronomie, Auf den Hüugel 69, D-53121 Bonn, Germany (chenkel, ypwang, hfalcke@mpifr-bonn.mpg.de)
(2)European Southern Observatory, Casilla 19001, Santiago 19, Chile
(3) Purple Mountain Observatory, Academia Sinica, Nanjing 210008, China
(4)Department of Astronomy, University of Maryland, College Park, MD 20742-2421, USA (wilson@astro.umd.edu)
(5) Adjunct Astronomer, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
(6) Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 21218, USA (jbraatz@jupiter.harvard.edu)

Astronomy & Astrophysics (1998), in press


A systematic search for 22 GHz H2O megamaser emission is reported for 50 nearby (z < 0.15) FR I galaxies. No detection was obtained, implying that ultraluminous H2O masers (LH2O>103Lo) must be rare in early-type galaxies with FR\,I radio morphology. Despite higher radio core luminosities the detection rate for our sample is much lower than in similar surveys of late-type Seyfert galaxies. This puzzling difference between Seyferts and low-power radio galaxies could be explained in several ways: a) the maser emission is saturated and therefore independent of the radio core luminosity, b) the masers are unsaturated and the background continuum source is associated with the counter jet which is beamed away and relativistically dimmed in radio-galaxies, or c) the amount, kinematics, or the distribution of the molecular gas in the nuclei of Seyferts and radio galaxies is different. Further studies of maser properties may therefore hold a clue for morphological differences between active nuclei of Seyfert and early-type radio galaxies.

Please send an email request to chenkel@mpifr-bonn.mpg.de for a preprint. The paper is available in [(laa)LaTeX, PS] format.

Other publications can be found here.

Questions: Heino Falcke, hfalcke@mpifr-bonn.mpg.de