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

Abstract

We present the results of a Chandra X-ray survey of the eight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<z<0.1 and 90 Sunyaev-Zel'dovich-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 R 0.2 500 scaling like ( ) E z 2 . In the centers of clusters (  r R 0.01 500 ), we find significant deviations from self-similarity0.2 0.5 ), consistent with no redshift dependence. When we isolate clusters with overdense cores (i.e., cool cores), we find that the average overdensity 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 .

JVLA 1.5 GHz Continuum Observation of CLASH Clusters. I. Radio Properties of the BCGs

“…The energetics of the mechanical feedback have been systematically investigated at low and medium redshifts (Jetha et al 2007;Bîrzan et al 2008;Dunn & Fabian 2008;Blanton et al 2010;Dunn et al 2010;O'Sullivan et al 2011;Hlavacek-Larrondo et al 2012;Shin et al 2016) and pushed to the limits of detectability of X-ray cavities up to z ∼ 1.2 thanks to the Chandra follow-up of a sample of SZ-selected clusters (Hlavacek-Larrondo et al 2015). Cool cores are expected to be present from an early epoch (see Santos et al 2010;McDonald et al 2017) and a gentle feedback should be in place since then. However, while the average mechanical energy associated with feedback is sufficient to offset cooling, the process is expected to be intermittent.…”

Connecting optical and X-ray tracers of galaxy cluster relaxation

“…Correspondingly, the median A phot for NG clusters of 0.13 ± 0.03, suggesting that A phot 0.10 − 0.50 may be a useful dividing line between relaxed and unrelaxed clusters, depending on the desired level of purity. In McDonald et al (2017) a threshold of A phot < 0.10 is chosen to identify relaxed clusters, while this threshold was chosen arbitrarily we've shown here that this is a reasonable choice based on cluster velocity distribution measurements. The threshold used to identify unrelaxed clusters in McDonald et al (2017) is A phot > 0.50, which also shows excellent agreement with the dividing lines that we derive from velocity measurements.…”

“…In McDonald et al (2017) a threshold of A phot < 0.10 is chosen to identify relaxed clusters, while this threshold was chosen arbitrarily we've shown here that this is a reasonable choice based on cluster velocity distribution measurements. The threshold used to identify unrelaxed clusters in McDonald et al (2017) is A phot > 0.50, which also shows excellent agreement with the dividing lines that we derive from velocity measurements. The choice of A phot > 0.50 is motivated by simulations of cluster major mergers from Nurgaliev et al (2017) who suggest that A phot 0.2 − 0.6 is a useful threshold to identify disturbed clusters, again corresponding very closely to the range we determine in this work.…”

Mapping the gas thermodynamic properties of the massive cluster merger MOO J1142+1527 at z = 1.2

“…The data reduction is done using the Chandra Interactive Analysis of Observations software v4.10 based on the calibration database v4.8.0 provided by the Chandra X-ray Center. We follow the data reduction procedure detailed in [13] to reprocess the level 1 event files, remove flares from lightcurves, identify point sources, and estimate the X-ray background at the cluster location. The right panel of Fig.…”

“…We find a mean ICM spectroscopic temperature of T X = 8.63 ± 1.86 keV. We follow the methodology detailed in [13] to extract the cluster surface brightness profile S X in the 0.7-2.0 keV band in 20 annuli centered on both the X-ray peak and the X-ray centroid. This profile along with the spectroscopic temperature estimate are used to deproject the ICM density profile in Sect.…”