SIMBAD references

A systematic search for 22GHz H₂O megamaser emission is reported for 50 nearby (z≲0.15) FRI galaxies. No detection was obtained, implying that ultraluminous H₂O masers (L_H2_O>10³L_☉) must be rare in early-type galaxies with FRI radio morphology. Despite higher radio core luminosities the detection rate for our sample is 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 originate in a thin circumnuclear gas disk, so the `seed' radio continuum would come from the far jet which is relativistically dimmed 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 provide clues to the differences between radio-loud and radio-quiet AGN.