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.