Radio SNRs in the Magellanic Clouds as probes of shock microphysics

Abstract

A large number of supernova remnants (SNRs) in our Galaxy and galaxies nearby have been resolved in various radio bands. This radio emission is thought to be produced via synchrotron emission from electrons accelerated by the shock that the supernova ejecta drives into the external medium. Here we consider the sample of radio SNRs in the Magellanic Clouds. Given the size and radio flux of a SNR, we seek to constrain the fraction of shocked fluid energy in non-thermal electrons ($\epsilon_e$) and magnetic field ($\epsilon_B$), and find $\epsilon_e \epsilon_B \sim 10^{-3}$. These estimates do not depend on the largely uncertain values of the external density and the age of the SNR. We develop a Monte Carlo scheme that reproduces the observed distribution of radio fluxes and sizes of the population of radio SNRs in the Magellanic Clouds. This simple model provides a framework that could potentially be applied to other galaxies with complete radio SNRs samples.