The Interaction of Protostellar Winds with Their Environment

The time of protostellar wind breakout may be determined by the time-dependence of the infalling flow, rather than any sudden change in the driving wind. I examine the transition from pure infall to simultaneous infall and outflow, or pure outflow, in the context of rotating, inside-out collapse. Assuming a protostellar wind launched from the stellar surface, the breakout time is determined as a function of the wind’s mass-loss rate and speed, as well as the infall and rotation rate of the collapsing cloud core. The trapped phase consists of a wind sufficiently strong to push material back from the stellar surface, but too weak to carry the heavy, shocked infall out of the star’s gravitational potential. Unless the wind turns on impulsively, a significant fraction of the pre-breakout life of the protostar may be spent in this trapped wind phase in which gas is launched from the protostar but is pulled back, crashing onto the protostellar and disk surfaces. It may be that some “starless cores” contain as-yet undetected, very young accreting protostars, and that episodic luminosity fluctuations associated with this trapped wind could be observed.