The Salamander: A case study of the magnetic field and peculiar morphology of G309.8-2.6 through radio polarimetry

TL;DR

This study presents new radio polarimetry observations of the supernova remnant G309.8-2.6, revealing complex morphology and magnetic field structure, and integrates multiwavelength data to understand its environment and peculiar features.

Contribution

The paper provides the first detailed radio polarization images of G309.8-2.6, uncovering its unusual morphology and magnetic field configuration, and offers new insights into its interaction with the surrounding environment.

Findings

Revealed an S-shaped polarization morphology.

Detected a large-scale rotation measure gradient.

Constrained the magnetic field and environmental properties.

Abstract

Studying the interaction between core-collapse supernova remnants (SNRs) and their surrounding environments is essential to understanding the mechanism for energy transfer to the interstellar medium (ISM) and the intrinsic physical properties of these remnants. In this paper, we focus on G309.8-2.6. Our new observations reveal that this object includes an SNR shell with a relic pulsar wind nebula (PWN) that extends well beyond the emission that has been previously observed in X-rays. We present new radio continuum and polarization images of G309.8-2.6 from the Evolutionary Map of the Universe (EMU) and Polarization Sky Survey of the Universe's Magnetism (POSSUM) surveys with the Australian Square Kilometre Array Pathfinder (ASKAP). 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 rotation measure (RM) map shows a large-scale gradient or possible sign reversal, depending on the foreground RM. We reprocessed archival X-ray observations from Chandra and eROSITA, and retrieved archival H$\alpha$ and infrared observations. We performed a joint analysis of the multiwavelength data and proposed scenarios to explain the unusual shape. Our 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.