Galactic Supernova Remnants: an Updated Catalogue and Some Statistics
  A catalogue of 231 Galactic supernova remnants (SNRs) is presented, and the selection effects applicable to the identification of remnants at radio wavelengths are discussed. In addition to missing low surface brightness remnants, small angular size -- i.e. young but distant -- remnants are also missing from the current catalogue of Galactic SNRs. Several statistical properties of Galactic SNRs are discussed, including the surface-brightness/diameter (Sigma-D) relation. It is concluded that the wide range of intrinsic properties of Galactic remnants with known distances, together with the observational selection effects, means that use of the Sigma-D relation to derive diameters and hence distances for individual SNRs, or for statistical studies, is highly uncertain. The observed distribution of bright SNRs, which are thought to be largely free from selection effects, is also used to derive a simple model for the distribution of SNRs with Galactocentric radius. 
D. A. Green