X-ray Observations of Complex Temperature Structure in the Cool-core cluster Abell 85

TL;DR

This study uses high-fidelity X-ray temperature maps from Chandra and XMM-Newton to reveal complex temperature structures and potential shocks in the cool-core galaxy cluster Abell 85, indicating ongoing merging activity.

Contribution

It introduces an improved temperature mapping technique combining long-exposure XMM data with advanced binning, providing the most detailed temperature maps of Abell 85 to date.

Findings

Hot regions near subclusters suggest ongoing mergers.

Estimated Mach numbers around 1.9 indicate weak shocks.

No clear shock evidence near the radio relic.

Abstract

X-ray observations were used to examine the complex temperature structure of Abell 85, a cool-core galaxy cluster. Temperature features can provide evidence of merging events which shock heat the intracluster gas. Temperature maps were made from both \textit{Chandra} and \textit{XMM-Newton} obervations. The combination of a new, long-exposure \textit{XMM} observation and an improved temperature map binning technique produced the highest fidelity temperature maps of A85 to date. Hot regions were detected near the subclusters to the South and Southwest in both the \textit{Chandra} and \textit{XMM} temperature maps. The presence of these structures implies A85 is not relaxed. The hot regions may indicate the presence of shocks. The Mach numbers were estimated to be $\sim$1.9 at the locations of the hot spots. Observational effects will tend to systematically reduce temperature jumps, so the measured Mach numbers are likely underestimated. Neither temperature map showed evidence for a shock in the vicinity of the presumed radio relic near the Southwest subcluster. However, the presence of a weak shock cannot be ruled out. There was tension between the temperatures measured by the two instruments.