On the evolution of the entropy and pressure profiles in X-ray luminous galaxy clusters at z > 0.4
Résumé
Context. Galaxy clusters are the most recent products of hierarchical accretion over cosmological scales. The gas accreted from the cosmic field is thermalized inside the cluster halo. Gas entropy and pressure are expected to have a self-similar behaviour with their radial distribution following a power law and a generalized Navarro-Frenk-White profile, respectively. This has also been shown in many different hydrodynamical simulations. Aims. We derive the spatially resolved thermodynamical properties of 47 X-ray galaxy clusters observed with Chandra in the redshift range 0.4 0.75, where, in the central regions, we observe higher values of the entropy (by a factor of ~2.2) and systematically lower estimates (by a factor of ~2.5) of the pressure. The effective polytropic index, which retains information about the thermal distribution of the gas, shows a slight linear positive evolution with the redshift and concentration of the dark matter distribution. A prevalence of non-cool core, disturbed systems, as we observe at higher redshifts, can explain such behaviours. Key words: galaxies: clusters: intracluster medium / galaxies: clusters: general / X-rays: galaxies: clusters / intergalactic medium