# The XXL Survey: XVII. X-ray and Sunyaev-Zel'dovich Properties of the Redshift 2.0 Galaxy Cluster XLSSC 122

## TL;DR

This study presents detailed X-ray and Sunyaev-Zel'dovich observations of the galaxy cluster XLSSC 122 at redshift 2, providing new insights into its thermodynamic properties and confirming the evolution of cluster scaling relations.

## Contribution

First precise measurement of thermodynamic properties of a massive galaxy cluster at z~2 using X-ray and SZ data, confirming simple evolution of cluster scaling relations at high redshift.

## Key findings

- Measured temperature of 5.0 keV with metallicity Z/Z_sun=0.33
- Estimated mass M_500=(6.3±1.5)×10^13 M_sun
- Confirmed consistency with self-similar evolution models

## Abstract

We present results from a 100 ks XMM-Newton observation of galaxy cluster XLSSC 122, the first massive cluster discovered through its X-ray emission at $z\approx2$. The data provide the first precise constraints on the bulk thermodynamic properties of such a distant cluster, as well as an X-ray spectroscopic confirmation of its redshift. We measure an average temperature of $kT=5.0\pm0.7$ keV; a metallicity with respect to solar of $Z/Z_{\odot}=0.33^{+0.19}_{-0.17}$, consistent with lower-redshift clusters; and a redshift of $z=1.99^{+0.07}_{-0.06}$, consistent with the earlier photo-z estimate. The measured gas density profile leads to a mass estimate at $r_{500}$ of $M_{500}=(6.3\pm1.5)\times10^{13}M_{\odot}$. From CARMA 30 GHz data, we measure the spherically integrated Compton parameter within $r_{500}$ to be $Y_{500}=(3.6\pm0.4)\times10^{-12}$. We compare the measured properties of XLSSC 122 to lower-redshift cluster samples, and find good agreement when assuming the simplest (self-similar) form for the evolution of cluster scaling relations. While a single cluster provides limited information, this result suggests that the evolution of the intracluster medium in the most massive, well developed clusters is remarkably simple, even out to the highest redshifts where they have been found. At the same time, our data reaffirm the previously reported spatial offset between the centers of the X-ray and SZ signals for XLSSC 122, suggesting a disturbed configuration. Higher spatial resolution data could thus provide greater insights into the internal dynamics of this system.