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

• Published in: The Astrophysical Journal
• 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.
• Language: unknown
• Published: 2022
• Subjects: 79 ASTRONOMY AND ASTROPHYSICS; South Pole; South pole
• Online Access: http://www.osti.gov/servlets/purl/1373896; https://www.osti.gov/biblio/1373896; https://doi.org/10.3847/1538-4357/aa7740

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 deg2 survey. We combine this sample with previously-published Chandra observations of 49 massive X-ray-selected clusters at 0 < z < 0.1 and 90 SZ-selected clusters at 0.25 < z < 1.2 to constrain the evolution of the intracluster medium (ICM) over the past ~10 Gyr. We find that the bulk of the ICM has evolved self similarly over the full redshift range probed here, with the ICM density at r > 0.2R500 scaling like E(z) 2 . In the centers of clusters (r . 0.01R500), we find significant deviations from self similarity (ne ∝ 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 Xray, 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.