Planck intermediate results. VI: The dynamical structure of PLCKG214.6+37.0, a Planck discovered triple system of galaxy clusters

TL;DR

This paper investigates a triple galaxy cluster system discovered by Planck, using multi-wavelength data to analyze its physical properties, dynamics, and SZ signal, revealing an early-stage massive cluster formation within a supercluster.

Contribution

The study provides a detailed multi-wavelength analysis of a newly identified triple galaxy cluster system, improving understanding of its structure, dynamics, and SZ signal consistency, which was previously uncertain.

Findings

The three clusters are part of the same supercluster.

The SZ signal from Planck matches X-ray expectations within 1.2 sigma.

Evidence suggests the system is in early formation stages of a massive cluster.

Abstract

The survey of galaxy clusters performed by Planck through the Sunyaev-Zeldovich effect has already discovered many interesting objects, thanks to the whole coverage of the sky. One of the SZ candidates detected in the early months of the mission near to the signal to noise threshold, PLCKG214.6+37.0, was later revealed by XMM-Newton to be a triple system of galaxy clusters. We have further investigated this puzzling system with a multi-wavelength approach and we present here the results from a deep XMM-Newton re-observation. The characterisation of the physical properties of the three components has allowed us to build a template model to extract the total SZ signal of this system with Planck data. We partly reconciled the discrepancy between the expected SZ signal from X-rays and the observed one, which are now consistent at less than 1.2 sigma. We measured the redshift of the three components with the iron lines in the X-ray spectrum, and confirmed that the three clumps are likely part of the same supercluster structure. The analysis of the dynamical state of the three components, as well as the absence of detectable excess X-ray emission, suggest that we are witnessing the formation of a massive cluster at an early phase of interaction.