Environmental dependence of the fundamental plane of galaxy clusters

Galaxy clusters approximate a planar distribution in a three-dimensional pa rameter space that can be characterized, for example, by an optical luminos ity, half-light radius, and X-ray luminosity. We find the nearest neighbor clusters for those common to either of two previous fundamental-plane studi es 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 s hows that those with high central gas densities are systematically (2.5 sig ma) closer to neighbor clusters. These results suggest a possible explanati on for recent evidence that X-ray cooling flow clusters reside in crowded e nvironments.