Wide-field global VLBI and MERLIN combined monitoring of supernova remnants in M82

TL;DR

This study combines MERLIN and global VLBI observations to produce high-resolution images of supernova remnants in M82, tracking their evolution over 19 years and providing detailed measurements of their sizes, fluxes, and expansion behaviors.

Contribution

It presents the first combined MERLIN and global VLBI imaging of M82's supernova remnants, including a 19-year expansion analysis of the youngest remnant 43.31+59.3.

Findings

32 supernova remnants identified

Measured expansion and deceleration of 43.31+59.3

Provided detailed sizes and flux densities for all sources

Abstract

From a combination of MERLIN (Multi-Element Radio-Linked Interferometer Network) and global VLBI (Very Long Baseline Interferometry) observations of the starburst galaxy M82, images of 36 discrete sources at resolutions ranging from ~3 to ~80 mas at 1.7 GHz are presented. Of these 36 sources, 32 are identified as supernova remnants, 2 are HII regions, and 3 remain unclassified. Sizes, flux densities and radio brightnesses are given for all of the detected sources. Additionally, global VLBI only data from this project are used to image four of the most compact radio sources. These data provide a fifth epoch of VLBI observations of these sources, covering a 19-yr time-line. In particular, the continued expansion of one of the youngest supernova remnants, 43.31+59.3 is discussed. The deceleration parameter is a power-law index used to represent the time evolution of the size of a supernova remnant. For the source 43.31+59.3, a lower limit to the deceleration parameter is calculated to be 0.53+/-0.06, based on a lower limit of the age of this source.