A High Fidelity Sample of Cold Front Clusters from the Chandra Archive

TL;DR

This paper presents a carefully selected sample of galaxy clusters with cold fronts from the Chandra archive, analyzing their X-ray properties to understand merger activities and the nature of cold fronts in different dynamical states.

Contribution

It introduces a robust sample of nine cold front clusters selected solely based on surface brightness edges, and explores their merger states and implications for cluster evolution.

Findings

Existence of two subsamples: merging clusters and relaxed clusters with cold fronts.

Cold fronts can be the sole evidence of merger activity in some clusters.

Cold fronts may help distinguish between major and minor mergers.

Abstract

This paper presents a sample of "cold front" clusters selected from the Chandra archive. The clusters are selected based purely on the existence of surface brightness edges in their Chandra images which are modeled as density jumps. A combination of the derived density and temperature jumps across the fronts is used to select nine robust examples of cold front clusters: 1ES0657-558, Abell 1201, Abell 1758N, MS1455.0+2232, Abell 2069, Abell 2142, Abell 2163, RXJ1720.1+2638, and Abell 3667. This sample is the subject of an ongoing study aimed at relating cold fronts to cluster merger activity, and understanding how the merging environment affects the cluster constituents. Here, temperature maps are presented along with the Chandra X-ray images. A dichotomy is found in the sample in that there exists a subsample of cold front clusters which are clearly mergers based on their X-ray morphologies, and a second subsample which harbor cold fronts, but have surprisingly relaxed X-ray morphologies, and minimal evidence for merger activity at other wavelengths. For this second subsample, the existence of a cold front provides the sole evidence for merger activity at X-ray wavelengths. We discuss how cold fronts can provide additional information which may be used to constrain merger histories, and also the possibility of using cold fronts to distinguish major and minor mergers.