Profile and Model of Jet

Top: Observed and model profiles for [S II] 6731 of knot #3 in the L 1551 jet. The spectra were extracted from a 2.5" box centered on the location of the knot in both cases. Bottom-left : A schematic of the pure bow shock model. The bow moves into an outward flowing medium at an angle of about 45 degrees to the line of sight. The spectrum predicted from this model is shown in the top panel. Bottom-right: A schematic of a situation where both the bow shock and the Mach disk heat the gas within knot 3. The highest excitation emission lines, such as those from [O III], should occur behind the shock where material enters at the highest velocity.