As a supernova remnant (SNR) evolves, any embedded pulsar wind nebula (PWN) will interact with the reverse shock from the remnant, leading to distorted PWN morphologies. In some cases, the pulsar escapes from the explosion site, leaving behind a “relic” PWN and forming a new compact nebula near its current position. The relic PWN G309.8−2.6 provides a unique opportunity to understand how PWNe evolve and interact with their parent SNRs. G309.8−2.6 was initially identified as an SNR candidate by in the Parkes 2.4 GHz survey, on the basis of its extended features and polarization signal. However, the object has many unusual characteristics, such as its lack of shell-type morphology and flat spectrum, indicating a potential classification as a PWN rather than a typical SNR.

New observations by Jing et al. reveal that this object includes an SNR shell with a relic PWN that extends well beyond the emission that has been previously observed in X-rays. They present new radio continuum and polarization images of G309.8−2.6 from the ASKAP EMU and POSSUM surveys. The images reveal the complex and peculiar morphology of G309.8−2.6. The linear polarization displays an atypical S-shaped morphology and a highly ordered magnetic field. The team reprocessed archival X-ray observations and performed a joint analysis of the multiwavelength data in order to propose scenarios to explain the unusual shape. This also led to the source being named “Salamander” based on its X-ray emission near the pulsar PSR J1357−6325, which resembles a salamander. The results place new constraints on the magnetic field of G309.8−2.6, including its environment, and demonstrate the power of polarization observations in probing the properties of SNRs. The figure at left above shows the total intensity image from EMU for a 1.5 x 1.5 degree region at 943 MHz with an angular resolution of 18 arcseconds. The illustration at right shows the main features of G309.8−2.6. The SNR here includes the relic PWN and the eastern shell outlined by the orange polygon.