A Statistical Analysis of Galactic Radio Supernova Remnants

Abstract

We present an revised table of 390 Galactic radio supernova remnants (SNRs) and their basic parameters. Statistical analyses are performed on SNR diameters, ages, spectral indices, Galactic heights and spherical symmetries. Furthermore, the accuracy of distances estimated using the $\Sigma$-D relation is examined. The arithmetic mean of the Galactic SNR diameters is $30.5$ pc with standard error $1.7$ pc and standard deviation $25.4$ pc. The geometric mean and geometric standard deviation factor of Galactic SNR diameters is $21.9$ pc and $2.4$, respectively. We estimate ages of 97 SNRs and find that the supernova (SN) birth rate to be lower than, but within $2\sigma$ of currently accepted values for SN birth rate. The mean spectral index of shell-type SNRs is $-0.51 \pm 0.01$ and no correlations are found between spectral indices and the SNR parameters of molecular cloud (MC) association, SN type, diameter, Galactic height and surface brightness. The Galactic height distribution of SNRs is best described by an exponential distribution with a scale height of $48 \pm 4$ pc. The spherical symmetry measured by the ovality of radio SNRs is not correlated to any other SNR parameters considered here or to explosion type.