H2O MEGAMASER EMISSION FROM FRI RADIO GALAXIES

Citation
C. Henkel et al., H2O MEGAMASER EMISSION FROM FRI RADIO GALAXIES, Astronomy and astrophysics (Berlin), 335(2), 1998, pp. 463-466
Citations number
25
Categorie Soggetti
Astronomy & Astrophysics
ISSN journal
00046361
Volume
335
Issue
2
Year of publication
1998
Pages
463 - 466
Database
ISI
SICI code
0004-6361(1998)335:2<463:HMEFFR>2.0.ZU;2-6
Abstract
A systematic search for 22 GHz H2O megamaser emission is reported for 50 nearby (z less than or similar to 0.15) FRI galaxies. No detection was obtained, implying that ultraluminous H2O masers (L-H2O > 10(3) L- .) must be rare in early-type galaxies with FR I radio morphology. Des pite higher radio core luminosities the detection rate for our sample is lower than in similar surveys of late-type Seyfert galaxies. This p uzzling 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 originate in a thin circumnuclear gas disk, so the 'se ed' radio continuum would come from the far jet which is relativistica lly dimmed or c) the amount, kinematics, or the distribution of the mo lecular gas in the nuclei of Seyferts and radio galaxies is different. Further studies of maser properties may provide clues to the differen ces between radio-loud and radio-quiet AGN.