Kinematics of the HH 111 jet from STIS spectra

We present a long-slit spectrum of the Herbig-Haro object HH 111, obtained with SITS on the Hubble Space Telescope. This spectrum has a spectral resolution of approx. 50 km/s, so it gives a good picture of the kinematical properties of the observed object at very high angular resolution. We find that some of the knots along the jet are associated with sudden drops in the radial velocity (modulus), confirming that the emission from the knots is formed in shocks. We interprt the observed position-velocity diagrams in terms of a model of a jet from a variable source, and we attempt to carry out a reconstruction of the ejection variability necessary for reproducing the observed kinematical structure.