HST and HSC Weak-lensing Study of the Equal-mass Dissociative Merger CIZA J0107.7+5408

TL;DR

This study uses weak-lensing, optical, and X-ray data to analyze the dissociative merger CIZA J0107.7+5408, revealing a bimodal mass distribution offset from X-ray peaks, indicating an equal-mass merger with consistent mass-to-light ratios.

Contribution

First detailed weak-lensing analysis of CIZA J0107.7+5408 showing a bimodal mass distribution aligned with galaxies but offset from X-ray peaks, confirming an equal-mass dissociative merger.

Findings

Bimodal mass distribution consistent with galaxy distribution

Masses of subclusters approximately 2.8 and 3.1 x 10^{14} solar masses

Mass-to-light ratios are similar and typical for galaxy clusters

Abstract

A dissociative merger is formed by the interplay of ram pressure and gravitational forces, which can lead to a spatial displacement of the dark matter and baryonic components of the recently collided subclusters. CIZA J0107.7+5408 is a nearby (z=0.105) dissociative merger that hosts two X-ray brightness peaks and a bimodal galaxy distribution. Analyzing MMT/Hectospec observations, we investigate the line-of-sight and spatial distribution of cluster galaxies. Utilizing deep, high-resolution Hubble Space Telescope Advanced Camera for Surveys imaging and large field-of-view Subaru Hyper-Suprime-Cam observations, we perform a weak-lensing analysis of CIZA J0107.7+5408. Our weak-lensing analysis detects a bimodal mass distribution that is spatially consistent with the cluster galaxies but significantly offset from the X-ray brightness peaks. Fitting two NFW halos to the lensing signal, we find an equal-mass merger with subcluster masses of $M_{200,NE}=2.8^{+1.1}_{-1.1}\times10^{14}$ M$_\odot$ and $M_{200,SW}=3.1^{+1.2}_{-1.2}\times10^{14}$ M$_\odot$. Moreover, the mass-to-light ratios of the subclusters, $(M/L)_{NE}=571^{+89}_{-91}$ $M_\odot/L_{\odot,B}$ and $(M/L)_{SW}=564^{+87}_{-89}$ $M_\odot/L_{\odot,B}$, are found to be consistent with each other and within the range of mass-to-light ratios found for galaxy clusters.