The Bautz-Morgan Classification of Clusters Containing Radio Galaxies

Clusters and groups of galaxies containing 3CR and 4C radio sources are classified using the Bautz–Morgan (BM) system. It is established that powerful radio galaxies occur much more commonly in BM class I clusters than in any other class. As the radio source is usually associated with the optically brightest galaxy in the cluster, it is concluded that in BM class I clusters the integrated radio lifetime of the brightest galaxy is greater than in other classes of cluster. The absolute optical magnitudes and optical spectra of the radio galaxies in clusters do not vary significantly with BM class. This suggests that the preferential occurrence of radio sources in BM class I clusters may be associated with some property of the cluster.