Proper Motions And Variability Of The H[TINF]2[/TINF] Emission In The HH 46/47 System

We report here on the first proper motion measurements of molecular hydrogenemission features in the Herbig-Haro 46/47 outflow. Assuming a distance of 350pc to this flow, the inferred tangential velocities range from a few tens toalmost 500 km/s . The highest velocities are observed for H2 knots either in,or close to, the jet/counterjet axes. Knots constituting the wings of the largescale H2 bow (see, for example, Eisl\"offel et al. 1994) are found to move muchmore slowly. These results appear to be in agreement with recent numericalsimulations of H2 emission from pulsed jets. We also report the first detectionof variability in H2 features for a young stellar object (YSO) outflow. It wasfound that several H2 knots significantly changed their luminosity over the 4year timebase used to conduct our study. This is in line with current estimatesfor the cooling time of gas radiating shocked H2 emission in YSO environments.Comment: 2 figure