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 G320.4– 01.2 (MSH 15–52) and the coincident young pulsar B1509–58 made with the Australia Telescope Compact Array. Based on a comparison between X-ray and radio observations, we argue that the two main radio components of G320.4–01.2 are a single supernova remnant (SNR), which H i absorption indicates is at a distance of 5.2± 1.4 kpc. A high-resolution correspondence between radio and X-rays argues that the pulsar is interacting with the SNR via an opposed pair of collimated outflows. The outflow itself is seen as an elongated X-ray feature surrounded by a highly polarized radio sheath, while the 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 associated and have an age of ∼1700 yr. We propose that the SNR resulted from a high-energy or low-mass supernova which occurred near the edge of an elongated cavity. Such a model can account for the SNR’s bilateral appearance, its large apparent age, the significant offset of the pulsar from the SNR’s centre and the faintness of the pulsar-powered nebula at radio wavelengths.