2001A&A...377..285D

Near-Infrared echelle spectra of the Herbig-Haro knots F-P in the western lobe of the HH 111 outflow are presented. 10 adjacent, parallel slit positions were observed so that the kinematics could be mapped across the width of the flow. We find broad (FWZI∼100km/s), two-component H₂ profiles in the knots nearest the source; the profiles converge to a single, intermediate-velocity peak (V_LSR ∼50km/s) at knot P. The kinematic signature of the HH 111 jet in H₂ is very similar to that seen at optical wavelengths (from both radial and tangential velocity meaurements). In conjunction with published proper-motion (knot/shock pattern speed) measurements, we interpret the data in terms of a simple geometrical bow shock model. The model infers a high pre-shock velocity, of the order of 200-250km/s, with H₂ excitation in the extended bow wings in knots L, H and F, though exclusively near the bow head in knot P, with probably C-type shock excitation throughout.