Environmental Dependence of the Fundamental Plane of Galaxy Clusters.
Galaxy clusters approximate a planar distribution in a three-dimensional parameter space that can be characterized, for example, by an optical luminosity, half-light radius, and X-ray luminosity. We find the nearest neighbor clusters for those common to either of two previous fundamental-plane studies and a high-quality cluster redshift catalog. Examining scatter about one plane in parameter space, we find a 2 sigma result that it is dependent on the nearest neighbor distance. Study of another sample of X-ray clusters shows that those with high central gas densities are systematically (2.5 sigma) closer to neighbor clusters. These results suggest a possible explanation for recent evidence that X-ray cooling flow clusters reside in crowded environments.