# Two merging galaxy clusters with very hot shock fronts observed shortly before pericentric passage

## TL;DR

This study analyzes two merging galaxy clusters with very hot shock fronts, using X-ray data and hydrodynamic simulations to determine their merger stage and geometry, revealing they are observed shortly before core collision.

## Contribution

The paper provides detailed X-ray analysis and hydrodynamic models of two galaxy cluster mergers, estimating their Mach numbers, shock properties, and merger stages with new observational and simulation data.

## Key findings

- Both clusters host among the hottest known merger shocks.
- The clusters are observed shortly before core passage, at specific inclination angles.
- Simulations estimate the merger timelines and geometries accurately.

## Abstract

We present a detailed analysis of two merging clusters, from XMM-\textit{Newton} X-ray archival data: PLCKESZ G036.7+14.9 ($z=0.15$; hereafter G036) and PLCK G292.5+22.0 ($z=0.30$; hereafter G292). We notice that the intracluster medium is heated as a result of the merger, and we find evidence for a merger shock in the region between both subcluster haloes. X-ray observations confirm that the shocks in these systems are among the hottest known in the literature. From the ICM analysis of temperature discontinuity, the Mach numbers were determined to be $M_{\rm G036}=1.3$ and $M_{\rm G292}=1.5$ for G036 and G292, respectively. In this paper, for each cluster, we propose a hydrodynamic model for the merger as a whole, compatible with their diffuse X-ray emission and temperature maps. The simulations suggest that both clusters are observed shortly before pericentric passage. Our simulation results indicate that the merger of the G036 system is seen at an inclination of 50$^{\circ}$ (the angle between the plane of the orbit and the plane of the sky), and merely 50 Myr prior to the pericentric passage. In the case of G292, the subclusters would be merging not far from the plane of the sky ($i=18^{\circ}$) and are observed 150\,Myr before the two cores collide.