The NuSTAR, XMM-Newton, and Suzaku view of A3395 at the intercluster filament interface

TL;DR

This study uses multi-telescope X-ray data to analyze the interface between galaxy cluster A3395 and an intercluster filament, revealing cooler, denser gas indicative of early merger stages and demonstrating a novel background disentangling technique.

Contribution

Developed a new method to separate scattered light background in NuSTAR data, enabling accurate temperature measurements of the intracluster medium despite contamination.

Findings

The cluster-filament interface shows no heated plasma, indicating early merger phase.

The gas at the interface is cool, dense, and low entropy, suggesting cooling and turbulence.

NuSTAR and XMM-Newton temperature measurements are consistent within contamination limits.

Abstract

Galaxy clusters are the largest virialized objects in the universe. Their merger dynamics and their interactions with the cosmic filaments that connect them are important for our understanding of the formation of large-scale structure. In addition, cosmic filaments are thought to possess the missing baryons in the universe. Studying the interaction of galaxy clusters and filaments therefore has the potential to unveil the the origin of the baryons and the physical processes that occur during merger stages of galaxy clusters. In this paper, we study the connection between A3395 and the intercluster filament with NuSTAR, XMM-Newton, and Suzaku data. Since the NuSTAR observation is moderately contaminated by scattered light, we present a novel technique developed for disentangling this background from the emission from the intracluster medium. We find that the interface of the cluster and the intercluster filament connecting A3395 and A3391 does not show any signs of heated plasma, as was previously thought. This interface has low temperature, high density, and low entropy, thus we suggest that the gas is cooling, being enhanced by the turbulent or tidal 'weather' driven during the early stage of the merger. Furthermore, our temperature results from the NuSTAR data are in agreement with those from XMM-Newton, and from joint NuSTAR and XMM-Newton analysis for a region with ~25% scattered light contamination within 1 sigma. We show that the temperature constraint of the intracluster medium is valid even when the data are contaminated up to ~25% for ~5 keV cluster emission.