STRUCTURE AND CHEMISTRY OF ORION-S

We present interferometric observations of the SiO J = 2-1, (HCO+)-C-13 J = 1-0, HC3N J = 11-10, CH30H J(K) = 2(0)-1(0), and SO2 J(KpK0) = 8(17)-8(08) transitions along with the lambda = 3.1 mm continuum toward the young stellar object Orion S. The HC3N and (HCO+)-C-13 emission trace similar spatial and velocity distributions which are extended and follow the Orion molecular ridge. The SiO emission is more spatially confined, peaking to the west of the )lambda = 3.1 mm continuum source, while the CH30H emission peaks to the southwest. Weak SO2 emission was detected southeast of the continuum source position. Column densities and fractional abundances are derived for each species at different positions in the region. In general, the molecular abundances near the continuum source are similar to those in the quiescent material near IRc 2, but the abundances decrease toward the continuum source position indicating localized depletions of at least a factor of 3 in our approximately 10'' beam. The presence of strong SiO emission with much weaker SO2 emission is interpreted as resulting from high-velocity shock interactions between the outflow from Orion S and the surrounding cloud. The apparent molecular depletions directly toward Orion S, and the similarity of abundances between the Orion S region and quiescent ridge material, suggest that Orion S is at an early stage of chemical evolution, prior to when substantial chemical differentiation occurs.