“EVALUATION OF THE DYNAMICAL STATE OF THE HIGHREDSHIFT GALAXY CLUSTER SPT-CL J2215-3537”

Abstract

The accurate determination of the dynamical state of galaxy clusters is critical for cluster cosmology, as near-equilibrium processes in the intracluster medium of dynami- cally relaxed systems enable the derivation of the mass distribution and other important scaling relations with minimal uncertainties. Recently the galaxy cluster SPT-CL J2215- 3537 (z = 1.16) has been identified as one of the most distant relaxed cluster using the symmetry–peakiness–alignment (SPA) criterion, which consists in the construction of X-ray morphological statistics to assess the degree of relaxation. However, SPT-CLJ0615- 5746 (z = 0.97), which was previously marked as relaxed by the SPA treatment, showed signs to be in a merging state when analyzed by the intracluster light fraction and tradi- tional X-ray analysis. The present work aims to evaluate the dynamical state of SPT-CL J2215-3537 through X-ray spectral and imaging analyzes. The characterization of the thermodynamical properties of the intracluster medium and its morphological features reveals signatures of sloshing cold fronts in the SE-NW axis. We find a ghost cavity candidate and estimate its mechanical power as log10{Pcav/(10^42 erg/s)} = 2.66+-0.23, indicanting that radiative cooling strongly exceeds AGN feedback heating. The results from our combined analysis suggest that SPT-CL J2215-3537 is mildly disturbed. We use the feedback-regulated precipitation framework to show that the cluster’s core is likely in a transient state towards a stable cooling-feedback cycle within the next ~ 100+-70 Myr. We additionally recalculate traditional X-ray morphological parameters and present a discussion of its limitations for high-redshift clusters.