ABUNDANCES OF HYDROGEN-SULFIDE IN STAR-FORMING REGIONS

Interstellar hydrogen sulfide (H2S) and its isotopic variant H234S have been observed toward several star-forming regions via their 110-101 transitions at 2 mm, using the FCRAO telescope. In sources where both isotopic species H2S and H234S were observed, column densities of ∼1016 cm-2 were measured. Column density lower limits of ∼1014 cm-2 for H2S were found for other sources, where only the main isotopic line was observed. The fractional abundances of H2S relative to molecular hydrogen appear to be enhanced by at least an order of magnitude relative to quiescent cloud values (- 10-9) for many of the observed sources. Such enhancement toward star-forming clouds suggests that some process involving elevated temperature aids in producing this species; this could be gas-phase reactions, grain-related processes, or both.