The jet/environment density ratio of stellar jets.

Abstract

The jet-to-environment density ratio is one of the most important, and possibly the most uncertain of the parameters of jets from young stars. The authors present a simple method for determining this density ratio, which can be used for objects in which the bowshock and the terminal Mach disk (or "jet shock") in the head of the jet are observationally resolved in Hα and [S II] λλ6717+31 narrowband images. The authors' method also yields values for the shock velocities of the bowshock and the jet shock. An application of this method to the HH 111 observations of Reipurth, Raga, Heathcote (1992) gives a jet-to-environment density ratio of 23 at the position of HH 111V. The values obtained for the shock velocities are v_js ≈ 25 km s^-1 and v_bs ≈ 110 km s^-1 for the jet shock and for the bowshock (respectively). The obtained density ratio and shock velocities are consistent with ram pressure balance across the working surface, which gives credibility to the identification of the jet shock and bowshock emission in the HH 111V observations.