SNR G320.4-01.2 and PSR B1509-58: new radio observations of a complex interacting system

We describe radio continuum and spectral-line observations of the source G3 20.4-01.2 (MSH 15-52) and the coincident young pulsar B1509-58 made with th e Australia Telescope Compact Array. Based on a comparison between X-ray an d radio observations, we argue that the two main radio components of G320.4 -01.2 are a single supernova remnant (SNR), which Hr absorption indicates i s at a distance of 5.2 +/- 1.4 kpc. A high-resolution correspondence betwee n radio and X-rays argues that the pulsar is interacting with the SNR via a n opposed pair of collimated outflows. The outflow itself is seen as an elo ngated X-ray feature surrounded-by a highly polarized radio sheath, while t he interaction with the SNR manifests itself as a ring of radio/X-ray knots within the optical nebula RCW 89. We reject the hypothesis that the pulsar outflow powers the entire RCW 89 region. SNR G320.4-01.2 and PSR B1509-58 agree in distance and in rotation measure, and appear to be interacting. We thus conclude that the two objects are as sociated and have an age of less than or similar to 1700 yr. We propose tha t the SNR resulted from a high-energy or low-mass supernova that occurred n ear the edge of an elongated cavity. Such a model can account for the bilat eral appearance of the SNR, its large apparent age, the significant offset of the pulsar from the centre of the SNR and the faintness of the pulsar-po wered nebula at radio wavelengths.