2011ApJ...740L...3V

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 CH₃ OH emitting only at relatively low outflow velocities whereas H₂ O 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.