Fast molecular shocks. II - Emission from fast dissociative shocks

Abstract

The line radiations emitted in the cooling gas behind a fast dissociative shock are studied. The intensities emitted in highrotational transitions of the neutral molecules CO, SiO, HCN, CN, NO,and SO are estimated, as well as in rovibrational transitions of themolecular ions HeH(+) and OH(+) in radio recombination lines of atomichydrogen and in fine-structure transitions of C, C(+), O, and Si(+). Thepredictions are compared with the observed intensities of line emissionfrom the Orion-KL region. For Orion-KL the observations do not exclude,but probably do not require, the presence of a fast dissociative shock.Emission from SiO in high-J rotational states and from vibrationallyexcited OH(+), HeH(+), HeH(+), and SO(+) may be detectable fromdissociative shocks under suitable conditions of preshock density andshock velocity; such emission may prove to be a useful diagnostic probeof fast shock activity.