The bow shock and jet in L 483

The physical parameters of jets are still poorly understood. Here we present long slit spectra of the molecular hydrogen emission from the jet powered by the young stellar object in L483, from which we obtain details of the jet structure and shock velocities. The jet has a knotty structure, and, in addition, weaker emission is seen between the knots, so that emission is observed along the full length of the jet. The H 2 emission from the bright bow shock at the end of the jet has an excitation temperature of 2200 K, and is consistent with a bow C–shock of speed 40–45 km s −1. Lower speed J–shocks, which could also match the H 2 emission, are ruled out by a lower limit on the shock speed provided by an analysis of the CO emission from the outflow. Assuming a jet velocity of ∼ 200 km s −1 , this shock velocity indicates that the jet from L483 has a density of about 10 times less that the medium into which it is propagating. The H 2 knots are possibly due to jet instabilities, or could be indicative of episodic activity. Emission from between the knots could be indicative of a partially molecular jet, entrainment in a mixing layer, or unresolved sub-knots. These possibilities, and how they impact on outflow models, are discussed.