THE CLUSTERING OF RADIO GALAXIES

We suggest that the strong clustering of radio galaxies, which is intermediate in strength between the clustering of individual galaxies and that of rich clusters, originates in the preferential location of the radio galaxies in groups of galaxies of intermediate richness. The radio galaxies then trace the same large-scale structure traced by the parent groups. At low redshifts, radio galaxies of intermediate radio power arc located in poor groups of median richness approximately 13L] galaxies. Radio galaxies of the F-R I type at intermediate radio power inhabit richer groups, with median richnesses approximately 33L] galaxies. The correlation scale lengths of the radio galaxies, approximately 11 h-1 Mpc and approximately 15 h-1 Mpc, respectively, for these galaxy types, are consistent with the richness-dependent cluster correlation function for the above richness of the parent groups. Powerful radio richness of the parent groups. Powerful radio galaxies at z approximately 0.5, suggested to be located in rich environments of approximately 33L] galaxies, arc also expected to exhibit strong correlations and thus may be a good tracer of large-scale structure at these high redshifts.