L1157-B1: WATER AND AMMONIA AS DIAGNOSTICS OF SHOCK TEMPERATURE
We investigate the origin and nature of the profiles of water and ammonia observed toward the L1157-B1 clump as part of the HIFI CHESS survey using a new code coupling a gas-grain chemical model with a parametric shock model. First results from the unbiased survey reveal different molecular components at different excitation conditions coexisting in the B1 bow shock structure, with NH3, H2CO, and CH3OH emitting only at relatively low outflow velocities whereas H2O shows bright emission at high velocities. Our model suggests that these differences are purely chemical and can be explained by the presence of a C-type shock whose maximum temperature must be close to 4000 K along the B1 clump.