Sulphur-bearing molecules as tracers of shocks in interstellar clouds

Abstract

We have computed two-fluid MHD models of shocks propagating in molecular clouds of density in the n(H) range of 10 exp 4 to 10 exp 6/cu cm, with speeds of 5-40 km/s. Attention has been paid to the chemistry of sulphur-bearing species, particularly SO, SO2, CS, and H2S. We find that the fractional abundance of H2S is enhanced within the shock, while those of SO and especially SO2 can be enhanced both within the shock and for large distances (up to 10 exp 18 cm) into the postshock gas. The fractional abundance of CS, on the other hand, remains roughly constant. The relevance of these results to observations of outflows in molecular clouds is mentioned.