Witnessing a merging bullet being stripped in the galaxy cluster, RXCJ2359.3-6042

TL;DR

This paper reports the discovery and analysis of a unique merging galaxy cluster, RXCJ2359.3-6042, where a compact bullet penetrates a larger cluster, revealing details of the merger process and associated shock heating.

Contribution

It provides the first detailed X-ray observational evidence of a bullet penetrating a galaxy cluster without disruption, including temperature and metallicity profiles of the merging components.

Findings

Identification of a cold, metal-rich bullet at 1.55 keV

Detection of a shock-heated region east of the cluster

Mass estimate of about 2 x 10^14 solar masses within r500

Abstract

We report the discovery of the merging cluster, RXCJ2359.3-6042, from the REFLEX II cluster survey and present our results from all three detectors combined in the imaging and spectral analysis of the XMM-Newton data. Also known as Abell 4067, this is a unique system, where a compact bullet penetrates an extended, low density cluster at redshift z=0.099 clearly seen from our follow-up XMM-Newton observation. The bullet goes right through the central region of the cluster without being disrupted and we can clearly watch the process how the bullet component is stripped of its layers outside the core. There is an indication of a shock heated region in the East of the cluster with a higher temperature. The bulk temperature of the cluster is about 3.12 keV implying a lower mass system. Spearheading the bullet is a cool core centred by a massive early type galaxy. The temperatures and metallicities of a few regions in the cluster derived from the spectral analysis supports our conjecture based on the surface brightness image that a much colder compact component at 1.55 keV with large metallicity (0.75 Zsol) penetrates the main cluster, where the core of the infalling component survived the merger leaving stripped gas behind at the centre of the main cluster. We also give an estimate of the total mass within r500, which is about 2e14Msol from the deprojected spherical-beta modelling of the cluster in good agreement with other mass estimates from the M--Tx and M-sigma_v relations.