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arXiv · 1702.05094

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

M. McDonald·S. W. Allen·M. Bayliss·B. A. Benson·L. E. Bleem·M. Brodwin·E. Bulbul·J. E. Carlstrom·W. R. Forman·J. Hlavacek-Larrondo·G. P. Garmire·M. Gaspari·M. D. Gladders·A. B. Mantz·S. S. Murray
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Abstract

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 0 0.2R500 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).

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M. McDonald, S. W. Allen, M. Bayliss, B. A. Benson, L. E. Bleem, M. Brodwin, E. Bulbul, J. E. Carlstrom, W. R. Forman, J. Hlavacek-Larrondo, G. P. Garmire, M. Gaspari, M. D. Gladders, A. B. Mantz, S. S. Murray. 2017-02-16. The Remarkable Similarity of Massive Galaxy Clusters From z~0 to z~1.9. https://doi.org/10.3847/1538-4357%2Faa7740

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