# Multi-wavelength Analysis of the Merging Galaxy Cluster A115

## TL;DR

This study provides a comprehensive multi-wavelength analysis of the merging galaxy cluster A115, revealing its substructure, mass distribution, and the effects of collision-induced disruption.

## Contribution

It offers the first detailed weak-lensing mass measurements of A115's subclusters and compares them with X-ray and spectroscopic data, highlighting collision effects.

## Key findings

- Weak-lensing masses are 3-10 times lower than X-ray and spectroscopic estimates.
- A115 consists of two subclusters with masses approximately 1.58 and 3.15 x 10^{14} solar masses.
- The total cluster mass is about 6.41 x 10^{14} solar masses.

## Abstract

A115 is a merging galaxy cluster at $z\sim0.2$ with a number of remarkable features including a giant ($\sim2.5$ Mpc) radio relic, two asymmetric X-ray peaks with trailing tails, and a peculiar line-of-sight velocity structure. We present a multi-wavelength study of A115 using optical imaging data from Subaru, X-ray data from $Chandra$, and spectroscopic data from the Keck/DEIMOS and MMT/Hectospec instruments. Our weak-lensing analysis shows that the cluster is comprised of two subclusters whose mass centroids are in excellent agreement with the two BCG positions ($\lesssim10$"). By modeling A115 with a superposition of two Navarro-Frenk-White halos, we determine the masses of the northern and southern subclusters to be $M_{200}=1.58_{-0.49}^{+0.56}\times 10^{14} \text{M}_{\odot}$ and $3.15_{-0.71}^{+0.79}\times 10^{14} \text{M}_{\odot}$, respectively. Combining the two halos, we estimate the total cluster mass to be $M_{200}=6.41_{-1.04}^{+1.08}\times10^{14} \text{M}_{\odot}$ at $R_{200}=1.67_{-0.09}^{+0.10}$ Mpc. These weak-lensing masses are significantly (a factor of 3-10) lower than what is implied by the X-ray and optical spectroscopic data. We attribute the difference to the gravitational and hydrodynamic disruption caused by the collision between the two subclusters.