Numerical hydrodynamics with a parallel integrated chemistry - I. A shear boundary layer

Abstract

Most astrophysical interfaces in the interstellar medium involve relative velocities between the various flows. Dynamical mixing will dominate the chemical and physical behaviour in these regions. To address this type of environment, we have developed a 2D numerical hydrodynamic code, employing adaptive grid techniques, which contains a large network of chemical reactions. This is currently the most sophisticated combined model of hydrodynamics and chemistry. In this first paper we apply the code to the study of the quasi-steady state chemical and physical structures (at high resolution) in a small portion of a shear interface between an atomic stellar wind and a cool diffuse cloud. The modelling suggests that although the abundances of most molecular species are not strongly enhanced in the interface, observationally significant column densities of certain species in highly ro-vibrationally excited states will be produced. We find that the most promising tracers of dynamical mixing include C, C+, CH, CH+, OH, CN, CO and HCO+.