An Arecibo survey for extragalactic hydroxyl absorption. I. Presentation of results.

A survey of 240 galaxies for hydroxyl absorption has been completed using the Arecibo Observatory. New results include five previously unpublished strong lines in NGC 2339, IC 860, IC 883, NGC 5859, and UGC 11905. Six additional possible lines where the signal-to-noise ratio is ⪉3 are also included. Spectra of the 1667 and 1665 MHz transition of OH are accompanied by 21 cm neutral-hydrogen spectra for these 11 galaxies. H I absorption appears at the same velocity as the hydroxyl features. In general, these galaxies are luminous IRAS sources and many are tidally interacting with a close companion or classified as mergers. Optical depths for the stronger 1667 MHz transition range from 0.004 to 0.27 and the hyperfine ratio is generally within the LTE limits. A large fraction of the lines (≡50%) are skewed toward the red, indicating an unusual velocity structure for the absorbing molecular disk.