Universal thermodynamic properties of the intracluster medium over two decades in radius in the X-COP sample

Abstract

The hot plasma in galaxy clusters is expected to be heated to high temperatures through shocks and adiabatic compression. The thermodynamical properties of the gas encode information on the processes leading to the thermalization of the gas in the cluster's potential well as well as non-gravitational processes such as gas cooling, AGN feedback and kinetic energy. In this work we present the radial profiles of the thermodynamic properties of the intracluster medium (ICM) out to the virial radius for a sample of 12 galaxy clusters selected from the Planck all-sky survey. We determine the universal profiles of gas density, temperature, pressure, and entropy over more than two decades in radius. We exploit jointly X-ray information from XMM and Sunyaev-Zel'dovich constraints from Planck to recover thermodynamic properties out to 2 R500. We provide average functional forms for the radial dependence of the main quantities and quantify the slope and intrinsic scatter of the population as a function of radius. We find that gas density and pressure profiles steepen steadily with radius, in excellent agreement with previous observational results. Entropy profiles beyond R500 closely follow the predictions for the gravitational collapse of structures. The scatter in all thermodynamical quantities reaches a minimum in the range [0.2-0.8] R500 and increases outwards. Somewhat surprisingly, we find that pressure is substantially more scattered than temperature and density. Our results indicate that once accreting substructures are properly excised, the properties of the ICM beyond the cooling region R > 0.3 R500) follow remarkably well the predictions of simple gravitational collapse and require little non-gravitational corrections.