THE INITIAL-STAGES OF AN HH JET CLOUD CORE COLLISION

We present a study of the initial evolution of the collision of an HH (Herbig-Haro) jet with a dense molecular cloud core. A simple analytical model shows that for a wide range of angles of incidence of the jet, the interaction will result in the formation of a reflected, less well collimated jet beam. Two-dimensional numerical simulations of the interaction of jets from constant and variable velocity sources with high density clouds (i.e., with infinite cloud-to-jet density ratios) are used to check the simple analytical model, and also to show the effect of the jet/cloud collision on the evolution of the internal working surfaces (formed by the source velocity variability). Predictions of [S II] emission maps from these models are also discussed. Finally, we present numerical simulations of jet/cloud interactions with finite cloud-to-jet density ratios, and discuss the observational implications of these models.