Kinematics of the HH 111 Jet from the Space Telescope Imaging Spectrograph

Abstract

We present a long-slit spectrum of the Herbig-Haro object HH 111,obtained with the Space Telescope Imaging Spectrograph on board theHubble Space Telescope. This spectrum has a spectral resolution ofapproximate to50 km s(-1), so it gives a good picture of the kinematicalproperties of the observed object at very high angular resolution. Wefind that some of the knots along the jet are associated with suddendrops in the radial velocity (modulus), confirming that the emissionfrom the knots is formed in shocks. We interpret the observedposition-velocity diagrams in terms of a model of a jet from a variablesource, and we attempt to carry out a reconstruction of the ejectionvelocity variability necessary for reproducing the observed kinematicalstructure.