CHEX-MATE: the intracluster medium entropy distribution in the gravity-dominated regime

• Main Authors: Riva, G, Pratt, G. W, Rossetti, M, Bartalucci, I, Kay, S. T, Rasia, E, Gavazzi, R, Umetsu, K, Arnaud, M, Balboni, M, Bonafede, A, Bourdin, H, De Grandi, S, De Luca, F, Eckert, D, Ettori, S, Gaspari, M, Gastaldello, F, Ghirardini, V, Ghizzardi, S, Gitti, M, Lovisari, L, Maughan, B. J, Mazzotta, P, Molendi, S, Pointecouteau, E, Sayers, J, Sereno, M, Towler, I
• Format: Journal Article
• Language: English
• Published: 15-10-2024
• Subjects: Physics - Cosmology and Nongalactic Astrophysics
• DOI: 10.48550/arxiv.2410.11947

We characterise the entropy profiles of 32 very high mass
($M_{500}>7.75\times10^{14}~M_{\odot}$) galaxy clusters (HIGHMz), selected from
the CHEX-MATE sample, to study the intracluster medium (ICM) entropy
distribution in a regime where non-gravitational effects are minimised. Using
XMM-Newton measurements, we measure the entropy profiles up to ~$R_{500}$ for
all objects. The scaled profiles exhibit large dispersion in the central
regions, but converge rapidly to the expectation from pure gravitational
collapse beyond the core. We quantify the correlation between the ICM
morphological parameters and scaled entropy as a function of radius, showing
that morphologically relaxed (disturbed) objects have low (high) central
entropy. We compare our data to other observational samples, finding
differences in normalisation which are linked to the average mass of the
samples in question. We find that a weaker mass dependence than self-similar in
the scaling (Am ~ -0.25) allows us to minimise the dispersion in the radial
range [0.3-0.8]$R_{500}$ for clusters spanning over a decade in mass. The
deviation from self-similarity is radially dependent and is more pronounced at
small and intermediate radii than at $R_{500}$. We also investigate the
distribution of central entropy $K_0$, finding no evidence for bimodality, and
outer slopes $\alpha$, which peaks at ~1.1. Using weak lensing masses, we find
indication for a small suppression of the scatter (~30%) beyond the core when
using masses derived from Yx in the rescaling. Finally, we compare to recent
cosmological numerical simulations from THE THREE HUNDRED and MACSIS, finding
good agreement with our observational data. These results provide a robust
observational benchmark in the gravity-dominated regime and will serve as a
future reference for samples at lower mass, higher redshifts, and for ongoing
work using cosmological numerical simulations.