ON METAL ABUNDANCE AND ENTROPY OF THE ICM: THE TWIN TRACERS OF BARYON EVOLUTION IN GALAXY CLUSTERS
Galaxy clusters are ideal systems for both cosmological and astrophysical studies, and their physical properties are determined by an interplay between baryonic and non-baryonic components. In particular, the main baryonic component of a cluster is the intracluster medium (ICM), the hot and diffuse gas that permeates the space between the galaxies in it. In this Thesis, we present the analysis of XMM-Newton observations of several galaxy clusters to investigate their ICM properties from two different but complementary perspectives: their chemo- and thermodynamics. The ICM is indeed chemically enriched with metals, and their distribution provides useful insights into chemical enrichment processes at large scales. Of particular interest are intermediate-mass systems (M500 = 1.5-3.5e14 Msun), the natural bridge between galaxy groups and massive clusters. After careful analysis of potential systematics in this mass range, we show that intermediate-mass clusters have similar iron-abundance profiles to more massive ones in their outskirts, supporting a common enrichment history for all systems, and iron yields intermediate between the two extremes of the cluster mass scale. The results of this Thesis will provide a valuable baseline for a larger project on intermediate-mass systems. We also investigated the ICM entropy distribution in massive clusters, in a regime where the hierarchical assembly drives the ICM properties, while non-gravitational effects are minimised. We selected 32 very massive (M500 > 7.75e14 Msun) systems from the CHEX-MATE sample and measured their entropy profiles out to their outer regions. The profiles show similar properties to other literature samples and, in combination with these, we constrained the effect of additional energy injection from non-gravitational processes on the ICM of clusters of different masses. These results provide a robust observational benchmark in the gravity-dominated regime and will serve as a future reference for samples at lower masses, higher redshifts, and for ongoing work using cosmological numerical simulations.
Settore PHYS-05/A - Astrofisica, cosmologia e scienza dello spazio
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