The Remarkable Similarity of Massive Galaxy Clusters From z~0 to z~1.9

• Main Authors: McDonald, M., Allen, S. W., Bayliss, M., Benson, B. A., Bleem, L. E., Brodwin, M., Bulbul, E., Carlstrom, J. E., Forman, W. R., Hlavacek-Larrondo, J., Garmire, G. P., Gaspari, M., Gladders, M. D., Mantz, A. B., Murray, S. S.
• Format: Text
• Language: unknown
• Published: arXiv 2017
• Subjects: Cosmology and Nongalactic Astrophysics astro-ph.CO; FOS Physical sciences; South Pole; South pole
• Online Access: https://dx.doi.org/10.48550/arxiv.1702.05094; https://arxiv.org/abs/1702.05094

We present the results of a Chandra X-ray survey of the 8 most massive galaxy clusters at z>1.2 in the South Pole Telescope 2500 deg^2 survey. We combine this sample with previously-published Chandra observations of 49 massive X-ray-selected clusters at 00.2R500 scaling like E(z)^2. In the centers of clusters (r<0.1R500), we find significant deviations from self similarity (n_e ~ E(z)^{0.1+/-0.5}), consistent with no redshift dependence. When we isolate clusters with over-dense cores (i.e., cool cores), we find that the average over-density profile has not evolved with redshift -- that is, cool cores have not changed in size, density, or total mass over the past ~9-10 Gyr. We show that the evolving "cuspiness" of clusters in the X-ray, reported by several previous studies, can be understood in the context of a cool core with fixed properties embedded in a self similarly-evolving cluster. We find no measurable evolution in the X-ray morphology of massive clusters, seemingly in tension with the rapidly-rising (with redshift) rate of major mergers predicted by cosmological simulations. We show that these two results can be brought into agreement if we assume that the relaxation time after a merger is proportional to the crossing time, since the latter is proportional to H(z)^(-1). : 14 pages, 12 figures, 3 tables. Submitted to ApJ. Comments welcome