The Sunyaev-Zel'dovich temperature of the intracluster medium

TL;DR

This paper compares the relativistic Sunyaev-Zel'dovich (SZ) temperature with X-ray temperature in galaxy clusters using simulations, finding SZ temperature is generally hotter and less affected by cooling and feedback.

Contribution

It demonstrates that SZ temperature measurements are less sensitive to cool gas and feedback effects, providing a robust method for probing cluster thermodynamics.

Findings

SZ temperature is within 10% of the virial temperature.

SZ temperature is consistently hotter than X-ray temperature.

SZ temperature is less affected by cooling and feedback processes.

Abstract

The relativistic Sunyaev-Zel'dovich (SZ) effect offers a method, independent of X-ray, for measuring the temperature of the intracluster medium (ICM) in the hottest systems. Here, using N-body/hydrodynamic simulations of three galaxy clusters, we compare the two quantities for a non-radiative ICM, and for one that is subject both to radiative cooling and strong energy feedback from galaxies. Our study has yielded two interesting results. Firstly, in all cases, the SZ temperature is hotter than the X-ray temperature and is within ten per cent of the virial temperature of the cluster. Secondly, the mean SZ temperature is less affected by cooling and feedback than the X-ray temperature. Both these results can be explained by the SZ temperature being less sensitive to the distribution of cool gas associated with cluster substructure. A comparison of the SZ and X-ray temperatures (measured for a sample of hot clusters) would therefore yield interesting constraints on the thermodynamic structure of the intracluster gas.