Updated radio $\Sigma-D$ relation for Galactic supernova remnants -- II

TL;DR

This paper updates the empirical radio surface-brightness-to-diameter relation for Galactic supernova remnants using a larger sample, compares it with theoretical models, and refines distance estimates for new remnants.

Contribution

It provides an improved $ ext{Σ--D}$ relation based on 110 SNRs, incorporating advanced fitting and smoothing techniques, and compares empirical results with simulations.

Findings

Best empirical-theoretical agreement when certain SNRs are filtered out.

Distances to 5 new remnants and 27 candidates are estimated.

Filtered sample yields more consistent $ ext{Σ--D}$ relation.

Abstract

In this paper we present the updated empirical radio surface-brightness-to-diameter ($\Sigma$--$D$) relation for Galactic supernova remnants (SNRs) calibrated using $110$ SNRs with reliable distances. We apply orthogonal fitting procedure and kernel density smoothing in $\Sigma-D$ plane and compare the results with the latest theoretical $\Sigma-D$ relations derived from simulations of radio evolution of SNRs. We argue that the best agreement between the empirical and simulated $\Sigma-D$ relations is achieved if the mixed-morphology SNRs and SNRs of both, low brightness and small diameter, are filtered out from the calibration sample. The distances to $5$ newly discovered remnants and $27$ new candidates for shell SNRs are estimated from our full and filtered calibration samples.