FORMALDEHYDE EMISSION IN GALAXIES

Nine detections of extragalactic emission in the 4.83 GHz 1(10)-1(11) formaldehyde transition are presented in addition to the only previously known extragalactic emission source in IC 4553. Formaldehyde emission occurs among both OH absorbers and emitters. In contrast with the high-detection rate of extragalactic sources in this survey, there are only a small number of Galactic sources with 4.83 GHz emission. Formaldehyde absorption has been found in one new source. A comparison has been made between the H2CO and OH properties of the galaxies. In analogy with the OH megamasers and as proposed for the IC 4553 formaldehyde megamaser emission line, low-gain amplification of radio continuum by foreground clouds in a molecular disk is also suggested for the new formaldehyde megamasers.