Frii Radio Sources in Rich Clusters of Galaxies

A sample of FRII radio sources in rich clusters of galaxies, both at high (z0.5) and low (z0) redshift, has been constructed to study the eeect of environment on radio sources. Comparisons are made between the properties of FRII sources in cluster and non-cluster environments, and between X-ray clusters with and without FRII sources. The principal results are the following: 1. Most low-redshift FRII sources in clusters appear to be similar to FRII sources in group or eld environments in terms of radio power, optical properties of the host galaxy, and nonthermal pressure of the radio bridge. Cygnus A is an exception with its high radio power and high nonthermal pressure. Most low-redshift clusters with FRII sources tend to lie at the lower end of cluster X-ray luminosity distribution, some having L x comparable to FRII sources in non-cluster environments. However, there are exceptions such as Cygnus A. Together, these results are in agreement with the model that it is the high-pressured intracluster medium that prevents FRII sources from forming in rich cluster environments at low-redshift. 2. High-redshift FRII sources are all quite similar to each other irrespective of their environments. While the radio powers and emission line luminosities of the host galaxies are higher on average than low-redshift FRII sources, there is also overlap, and the nonthermal pressures of the radio bridges appear to be similar to those of low-redshift FRII sources. Unfortunately, the X-ray data for high-redshift clusters with FRII sources are inconclusive because of the large number of upper bounds involved and possible AGN contribution to the X-ray luminosity. 3. The nonthermal pressures of the bridges of FRII sources appear to be similar to the thermal pressures of the ICM around them. This result, if connrmed by a larger sample, would allow FRII sources to be used as probes of their gaseous environments. The fact that most high-redshift FRIIs have similar nonthermal pressures to their low-redshift counterparts indicates that the gaseous environments around them are also similar, suggesting that most high-redshift clusters with FRII sources should be under-luminous X-ray emitters as are their low-redshift counterparts. Thus, the evolution in the clustering strength around FRII sources toward high-redshift is likely to be closely linked to an evolution of the state of the intracluster medium.