HyeongHan Kim (Yonsei University)

Weak-lensing View on Merging Galaxy Clusters in the Local Universe

Coma (z=0.0231) and Perseus (z=0.0179) are merging galaxy clusters in the local universe (z<<0.1) that exhibit various astrophysical phenomena including radio relics, halos, cold fronts, and X-ray shocks from extensive observations over a wide range of frequencies. However, the dark matter component remains elusive. In this talk, we report the dark matter structures in the Coma and Perseus clusters with the weak-lensing (WL) analysis using Subaru/Hyper Suprime-Cam imaging data. We achieve a robust WL analysis from a background galaxy sample that contains a large number density per physical area, high purity, and minimal impact from the line-of-sight large-scale structure, which permits us to investigate the low-density-contrast structures at low redshift. We report the WL detection of intracluster filaments in the Coma cluster that spatially align with the large-scale “cosmic web”. In the Perseus cluster, we report direct evidence of a major merger (~1:3) where the main and subhalos are connected by a significant mass bridge. With the MHD numerical simulation, we show that a high impact-parameter merger happened >5 Gyrs ago that reproduces the colossal cold front at ~700 kpc west and the mass bridge. We demonstrate that the WL analysis of galaxy clusters at low redshift regime is available and provides missing information on understanding cluster merger.