The nearest neighbor alignment of cluster X-ray isophotes

We examine the orientations of rich galaxy cluster X-ray isophotes with respect to their rich nearest neighbors using existing samples of Abell cluster position angles measured from Einstein and ROSAT observations. We study a merged subset of these samples using updated and improved positions and redshifts for Abell/ACO clusters. We find high confidence for alignment, which increases as nearest neighbor distance is restricted. We conclude that there is a strong alignment signal in all this data, consistent with gravitational instability acting on Gaussian perturbation.