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L1157, a molecular dark cloud with an embedded Class 0 protostar possessing abipolar outflow, is an excellent source for studying shock chemistry, includinggrain-surface chemistry prior to shocks, and post-shock, gas-phase processing.The L1157-B1 and B2 positions experienced shocks at an estimated ~2000 and 4000years ago, respectively. Prior to these shock events, temperatures were too lowfor most complex organic molecules to undergo thermal desorption. Thus, theshocks should have liberated these molecules from the ice grain-surfaces enmasse, evidenced by prior observations of SiO and multiple grain mantle speciescommonly associated with shocks. Grain species, such as OCS, CH3OH, and HNCO,all peak at different positions relative to species that are preferably formedin higher velocity shocks or repeatedly-shocked material, such as SiO and HCN.Here, we present high spatial resolution (~3") maps of CH3OH, HNCO, HCN, andHCO+ in the southern portion of the outflow containing B1 and B2, as observedwith CARMA. The HNCO maps are the first interferometric observations of thisspecies in L1157. The maps show distinct differences in the chemistry withinthe various shocked regions in L1157B. This is further supported throughconstraints of the molecular abundances using the non-LTE code RADEX (Van derTak et al. 2007). We find the east/west chemical differentiation in C2 may beexplained by the contrast of the shock's interaction with either cold, pristinematerial or warm, previously-shocked gas, as seen in enhanced HCN abundances.In addition, the enhancement of the HNCO abundance toward the the older shock,B2, suggests the importance of high-temperature O-chemistry in shocked regions.

CSO and CARMA Observations of L1157. II. Chemical Complexity in the Shocked Outflow