Interaction of Infall and Winds in Young Stellar Objects

The interaction of a stellar or disk wind with a collapsing environment holdspromise for explaining a variety of outflow phenomena observed around youngstars. In this paper we present the first simulations of these interactions.The focus here is on exploring how ram pressure balance between wind andambient gas and post-shock cooling affects the shape of the resulting outflows.In our models we explore the role of ram pressure and cooling by holding thewind speed constant and adjusting the ratio of the inflow mass flux to the windmass flux (Mdot_a/Mdot_w) Assuming non-spherical cloud collapse, we find thatrelatively strong winds can carve out wide, conical outflow cavities and thatrelatively weak winds can be strongly collimated into jet-like structures. Ifthe winds become weak enough, they can be cut off entirely by the infallingenvironment. We identify discrepancies between results from standard snowplowmodels and those presented here that have important implications for molecularoutflows. We also present mass vs. velocity curves for comparison withobservations.Comment: 35 pages, 11 figures (PNG and EPS