OBSERVATIONS OF H2S TOWARD OMC-1

Interstellar hydrogen sulfide (H2S) and its isotopic variant (H234S) have been observed toward several positions in OMC-1 via their 110-101 transitions near 168 GHz using the FCRAO 14 m telescope. We derive total column densities toward Orion(KL) for the extended ridge, for the plateau, and for the hot core, in addition to values for other positions in OMC-1. The fractional abundance of H2S (∼ 10-9) in the quiescent regions of OMC-1 seems to be difficult to explain by currently known ion-molecule reactions. The fractional abundance of H2S relative to H2 is enhanced by a factor of 1000 in the hot core and the plateau relative to the quiescent clouds. This enhancement may be a result of grain surface chemistry and/or of high-temperature gas-phase chemistry. From the nondetection of HDS in its 211-212 transition, we estimate the abundance ratio [HDS]/[H2S] ≤ 0.02 in the hot core.