Probing the Curious Case of a Galaxy Cluster Merger in Abell 115 with High Fidelity Chandra X-ray Temperature and Radio Maps

TL;DR

This study combines high-resolution X-ray and radio observations of galaxy cluster Abell 115 to analyze its merger dynamics, shock features, and radio relics, supported by numerical simulations.

Contribution

It provides new high-fidelity temperature and surface brightness maps and links observed shock features and radio relics to merger dynamics and simulations.

Findings

High X-ray temperature between subclusters indicates shock interaction.

Radio relic features are consistent with shock acceleration in mergers.

Numerical simulations support the proposed merger scenario.

Abstract

We present results from an X-ray and radio study of the merging galaxy cluster Abell 115. We use the full set of 5 Chandra observations taken of A115 to date (360 ks total integration) to construct high-fidelity temperature and surface brightness maps. We also examine radio data from the Very Large Array at 1.5 GHz and the Giant Metrewave Radio Telescope at 0.6 GHz. We propose that the high X-ray spectral temperature between the subclusters results from the interaction of the bow shocks driven into the intracluster medium by the motion of the subclusters relative to one another. We have identified morphologically similar scenarios in Enzo numerical N-body/hydrodynamic simulations of galaxy clusters in a cosmological context. In addition, the giant radio relic feature in A115, with an arc-like structure and a relatively flat spectral index, is likely consistent with other shock-associated giant radio relics seen in other massive galaxy clusters. We suggest a dynamical scenario that is consistent with the structure of the X-ray gas, the hot region between the clusters, and the radio relic feature.