PSZ2 G282.28+49.94, a recently discovered analogue of the famous Bullet Cluster

TL;DR

This paper studies the complex merging galaxy cluster PSZ2 G282.28+49.94, revealing its similarity to the Bullet Cluster and providing insights into dark matter properties through multi-wavelength observations.

Contribution

It presents the first detailed multi-wavelength analysis of PSZ2 G282.28+49.94, identifying its post-merger state and its analogy to the Bullet Cluster for dark matter studies.

Findings

The cluster shows a cometary ICM shape at z=0.56.

A large offset between X-ray peak and galaxy concentration suggests a recent merger.

The system is analogous to the Bullet Cluster, useful for dark matter constraints.

Abstract

We present a detailed study of the gas and galaxy properties of the cluster PSZ2 G282.28+49.94 detected in the Planck all-sky survey. The intracluster medium (ICM) of this object at z=0.56 exhibits a cometary-like shape. Combining Chandra and TNG observations, we characterised the spatially resolved thermodynamical properties of the gas and the spatial and velocity distribution of 73 galaxy members. The cluster structure is quite complex with an elongated core region containing the two brightest cluster galaxies and one dense group to the south-east. Since there is no velocity difference between the core and the south-east group, we suggest the presence of a merger along the plane of the sky. This structure is related to complex X-ray and radio features, and thus the merger has likely been caught during the post-merger phase. Comparing the distribution of the ICM and of member galaxies, we find a large offset of $\sim 350$ kpc between the position of the X-ray peak and the centre of a concentration of galaxies, preceding it in the likely direction of motion. This configuration is similar to the famous Bullet Cluster, leading us to dub PSZ2 G282.28+49.94 the "Planck bullet", and represents an ideal situation to provide astrophysical constraints to the self-interaction cross-section ($\sigma/m$) of dark matter particles. These results illustrate the power of a multi-wavelength approach to probe the merging scenario of such complex and distant systems.