The evolution of cluster radio galaxies from z=0 to z=0.8

A radio continuum survey of a complete sample of distant (z = 0.3-0.8) X-ra y-selected clusters has been conducted at 20 cm with the Very Large Array ( VLA). The targets for this survey are the complete sample of 19 distant clu sters found in the X-ray-selected Einstein Extended Medium Sensitivity Surv ey (EMSS) at z greater than or equal to 0.3 and delta greater than or equal to -20 degrees. This survey is complete to a limiting point-source radio p ower level of log P greater than or equal to 23.5 W Hz(-1) (H-0 = 75 km s(- 1) Mpc(-1) and q(0) = 0.1) out to 1/2 Abell cluster radius from the brighte st cluster galaxy close to the X-ray emission centroid. Of the total of 41 radio sources detected within 1/2 Abell radius, 23 are associated with gala xies in these clusters. Higher angular resolution mapping of these cluster radio galaxies provides details of their structure and morphology. A compar ison of the radio power levels, radio structure, position in the cluster, a nd the total number of these radio galaxies finds no evidence for any signi ficant differences compared to nearby rich cluster radio galaxies. The radi o luminosity function of distant cluster radio galaxies is statistically in distinguishable from that seen nearby. Taken together with the minimal evol ution seen in the number of rich clusters over the same time period, this p rovides substantial evidence for no evolution in the population of rich clu ster radio galaxies since z similar to 1/2. The results of this radio continuum survey differ from those studies that t ook the opposite approach, in which a radio-loud quasar or FR 2 radio galax y was used as a target for a rich cluster search. While those studies found numerous FR 2's and quasars in rich clusters at z similar to 1/2, this sur vey has found only FR 1-type sources. The difference between these two appr oaches may lie in the density of the intracluster medium (ICM) and the gala xy richness of the clusters in these two samples, with the current sample h aving the demonstrably denser ICMs and richer galaxy populations.