The morphology of clumps in molecular clouds excited by radiation from HH objects

We have investigated the influence of the radiation field from a Herbig-Haro object on a spherical clump, as the HH object passes by the clump. We have included a limited chemistry, and show column density maps of HCO+ and NH3 to represent the morphology of the predicted emission regions. The morphology is sensitive both to the orientation of the line of sight with respect to the HH trajectory and the clump, and to the extinction of the clump. Emission regions may appear barlike, arc-like, or clump-like. The fractional abundances within these structures are observationally significant. However, the clump is not significantly heated by the radiation, and no clump evaporation occurs during the passage of the HH object for cases where the trajectory does not impact on the clump.