Observational evidence suggests that clusters of galaxies are dynamic systems with rich evolutionary histories. These systems can therefore provide valuable information about the formation and evolution of structure in the universe. In order to extract this information properly, however, we need to have a clear understanding of the environments of clusters and the evolutionary processes they are experiencing. Towards this end, we undertook a detailed, multi-wavelength analysis of an x-ray bright sample of rich Abell clusters at z ~ 0.2. Specifically, we examined the characteristics of the x-ray emission and the presence of structure in this emission. We find that a large fraction of the sample possesses very complex core x-ray structures, implying an unrelaxed density distribution possibly driven by shocks, turbulence or bulk motions in the intracluster medium. We also surveyed the cluster-wide radio population at luminosities reaching down to low level AGN and star formation driven systems. The radio populations of the clusters are relatively diverse, despite the apparent homogeneity imposed by the sample selection criteria. The high and low luminosity radio galaxies are distributed throughout the cluster very differently, which is suggestive of the distinction between the nature of the radio emission in the two luminosity classes. We place constraints of the origin of the radio emission (either star formation or AGN driven) by using a combination of the optical morphologies and colors to classify the host galaxies. We also examine the possible properties which may be influential in determining the radio populations. Previous results indicate that the radio population may be linked to the dynamical state of the large scale environment in which the cluster resides. Our result support this hypothesis, noting an increase in the average fraction of radio galaxies for clusters with filamentary structure surrounding them. We find that the richness of the cluster may also play a role in shaping the radio galaxy population by influencing the amount of gas available for star formation in the cluster galaxies. We briefly discuss the interpretation of our results and their implications for models of structure formation in the universe.
- Pub Date:
- October 2000
- Physics: Astronomy and Astrophysics, Remote Sensing