Tracing shock type with chemical diagnostics - an application to L1157

The physical structure of a shock wave may take a form unique to its shock type, implying that the chemistry of each shock type is unique as well. In our recent paper, we investigate the different chemistries of J-type and C-type shocks using parameterised forms of their physical structures in order to identify unique molecular tracers of both shock types. We apply these diagnostics to the protostellar outflow L1157 to establish whether the B2 clump could host shocks exhibiting type-specific behaviour.

We find that a range of molecules including H2O and HCN have unique behaviour specific to a J-type shock, but that such differences in behaviour are only evident at low velocity and low density. We find that CH3OH is enhanced by shocks and is a reliable probe of the pre-shock gas density and is shock-type agnostic. Additionally, the fractional abundances within the B2 region are consistent with both C-type and J-type shock emission.