# Fully stripped? The dynamics of dark and luminous matter in the massive cluster collision MACSJ0553.4$-$3342

## TL;DR

This study investigates the complex dynamics of the galaxy cluster MACSJ0553, revealing it as a post-collision merger with unique features like dark matter-luminous matter alignment and extreme gas temperatures, providing insights into cluster collision physics.

## Contribution

The paper provides a detailed multiwavelength analysis of MACSJ0553, identifying it as a binary merger with specific features that enhance understanding of dark matter and gas interactions during cluster collisions.

## Key findings

- Unambiguous identification as a binary, post-collision merger.
- Separation of nearly 650 kpc between dark matter and X-ray peaks.
- Presence of extremely hot gas (kT > 15 keV) at merger ends.

## Abstract

We present the results of a multiwavelength investigation of the very X-ray luminous galaxy cluster MACSJ0553.4-3342 ($z = 0.4270$; hereafter MACSJ0553). Combining high-resolution data obtained with the Hubble Space Telescope and the Chandra X-ray Observatory with ground-based galaxy spectroscopy, our analysis establishes the system unambiguously as a binary, post-collision merger of massive clusters. Key characteristics include perfect alignment of luminous and dark matter for one component, a separation of almost 650 kpc (in projection) between the dark-matter peak of the other subcluster and the second X-ray peak, extremely hot gas (k$T > 15$ keV) at either end of the merger axis, a potential cold front in the east, an unusually low gas mass fraction of approximately 0.075 for the western component, a velocity dispersion of $1490_{-130}^{+104}$ km s$^{-1}$, and no indication of significant substructure along the line of sight. We propose that the MACSJ0553 merger proceeds not in the plane of the sky, but at a large inclination angle, is observed very close to turnaround, and that the eastern X-ray peak is the cool core of the slightly less massive western component that was fully stripped and captured by the eastern subcluster during the collision. If correct, this hypothesis would make MACSJ0553 a superb target for a competitive study of ram-pressure stripping and the collisional behaviour of luminous and dark matter during cluster formation.