An Off-Axis Galaxy Cluster Merger: Abell 0141

TL;DR

This study analyzes the structure of the galaxy cluster Abell 0141 using X-ray and optical data, revealing a bimodal, off-axis merger with moderate disturbances and no clear shock-heating evidence, indicating an early merger phase.

Contribution

The paper provides detailed X-ray morphological and temperature analysis of Abell 0141, highlighting its bimodal structure and early-stage off-axis merger dynamics, which was not previously characterized in detail.

Findings

Abell 0141 is a bimodal galaxy cluster with two sub-clusters separated by ~0.65 Mpc.

Both sub-clusters are moderately disturbed non-cool core structures.

Evidence suggests an off-axis collision with the cores intact, in an early merger phase.

Abstract

We present structural analysis results of Abell 0141 ($z$ = 0.23) based on X-ray data. The X-ray luminosity map demonstrates that Abell 0141 (A0141) is a bimodal galaxy cluster, which is separated on the sky by $\sim$ 0.65 Mpc with an elongation along the north-south direction. The optical galaxy density map also demonstrates this bimodality. We estimate sub-cluster ICM temperatures of 5.17$^{+0.20}_{-0.19}$ keV for A0141N and 5.23$^{+0.24}_{-0.23}$ keV for A0141S. We obtain X-ray morphological parameters w = 0.034$\pm{0.004}$, c = 0.113$\pm{0.004}$ and w = 0.039$\pm{0.004}$, c = 0.104$\pm{0.005}$ for A0141N and A0141S, respectively. The resulting X-ray morphological parameters indicate that both sub-clusters are moderately disturbed non-cool core structures. We find a slight brightness jump in the bridge region, and yet, there is still an absence of strong X-ray emitting gas between sub-clusters. We discover a significantly hotspot ($\sim$ 10 keV) between sub-clusters, and a Mach number $\textit{M}$ = 1.69$^{+0.40}_{-0.37}$ is obtained by using the temperature jump condition. However, we did not find direct evidence for shock-heating between sub-clusters. We estimate the sub-clusters' central entropies as $K_{0}$ > 100 keV cm$^{2}$, which indicates that the sub-clusters are not cool cores. We find some evidence that the system undergoes an off-axis collision; however, the cores of each sub-clusters have not yet been destroyed. Due to the orientation of X-ray tails of sub-clusters, we suggest that the northern sub-cluster moves through the south-west direction, and the southern cluster moves through the north-east direction. In conclusion, we are witnessing an earlier phase of close core passage between sub-clusters.