The Connection between Supernova Remnants and the Galactic Magnetic Field: A Global Radio Study of the Axisymmetric Sample

TL;DR

This study investigates the relationship between supernova remnant shapes and the Galactic magnetic field by modeling radio images of axisymmetric SNRs with two GMF models, revealing the significance of a vertical magnetic component.

Contribution

It introduces a comprehensive analysis of SNR morphologies in relation to the Galactic magnetic field using two models, highlighting the vertical component's role and proposing a new method for distance estimation.

Findings

Models with the Jansson & Farrar GMF reproduce SNR morphologies well.

Results support the existence of an off-plane, vertical magnetic field component.

The approach offers a new way to estimate SNR or GMF feature distances.

Abstract

The study of supernova remnants (SNRs) is fundamental to understanding the chemical enrichment and magnetism in galaxies, including our own Milky Way. In an effort to understand the connection between the morphology of SNRs and the Galactic magnetic field (GMF), we have examined the radio images of all known SNRs in our Galaxy and compiled a large sample that have an "axisymmetric" morphology, which we define to mean SNRs with a "bilateral" or "barrel"-shaped morphology, in addition to one-sided shells. We selected the cleanest examples and model each of these at their appropriate Galactic position using two GMF models, those of Jansson & Farrar (2012a), which includes a vertical halo component, and Sun et al. (2008) that is oriented entirely parallel to the plane. Since the magnitude and relative orientation of the magnetic field changes with distance from the sun, we analyse a range of distances, from 0.5 to 10 kpc in each case. Using a physically motivated model of a SNR expanding into the ambient GMF, we find the models using Jansson & Farrar (2012a) are able to reproduce observed morphologies of many SNRs in our sample. These results strongly support the presence of an off-plane, vertical component to the GMF, and the importance of the Galactic field on SNR morphology. Our approach also provides a potential new method for determining distances to SNRs, or conversely, distances to features in the large-scale GMF if SNR distances are known.