SHOCK CHEMISTRY IN THE YOUNG BIPOLAR OUTFLOW L1157

We present the first results from a recent survey of molecular lines i n L1157, a highly collimated bipolar molecular outflow driven by a cla ss 0 protostar. These observations are used to study the chemical alte rations produced by a violent, highly collimated outflow. Different mo lecular lines are observed to trace different components of the gas. S ome molecules (C3H2, N2H+, (HCO+)-C-13, DCO+) are abundant in the quie scent medium but are not observed at high velocities. Lines from these molecules are the best tracers of the concentration of dense gas arou nd the protostar. In addition, we find that some otherwise rare molecu les (e.g., SiO, CH3OH, H2CO, HCN, CN, SO, and SO2) are enhanced by at least an order of magnitude at the shocked region. Our observations pr ovide estimates of the enhancement factors for such species. Strong gr adients in the chemical composition are observed along the outflow blu e lobe, which could be due to the evolution in time of the chemical pr ocesses. We briefly discuss the chemistry of the most important molecu les, devoting special attention to the species that are thought to be abundant in interstellar ice mantles.