A Universal Luminosity Function for Radio Supernova Remnants
  We compile radio supernova remnant (SNR) samples from the literature for 19
nearby galaxies ranging from the SMC to Arp 220, and use this data to constrain
the SNR luminosity function (LF) at 20 cm. We find that radio SNR populations
are strikingly similar across galaxies. The LF can be described as a power law
with constant index and scaling proportional to a galaxy's star formation rate
(SFR). Unlike previous authors, we do not find any dependence of SNR luminosity
on a galaxy's global ISM density. The observed correlation between the
luminosity of a galaxy's brightest SNR and a galaxy's SFR can be completely
explained by statistical effects, wherein galaxies with higher SFR more
thoroughly sample the high-luminosity end of the SNR LF. The LF is well fit by
a model of SNR synchrotron emission which includes diffusive shock acceleration
and magnetic field amplification, if we assume that all remnants are undergoing
adiabatic expansion, the densities of star-forming regions are similar across
galaxies, and the efficiency of CR production is constant.
