PSZ2 G181.06+48.47 III: weak-lensing analysis and merging scenario reconstruction of a low-mass cluster with exceptionally-distant radio relics

TL;DR

This study presents the first weak-lensing analysis of the galaxy cluster PSZ2 G181.06+48.47, revealing its binary dark matter structure and proposing a merging scenario consistent with observed radio relics and numerical simulations.

Contribution

It provides the first weak-lensing mass measurement and merging scenario reconstruction for PSZ2 G181.06+48.47, combining observational data with numerical simulations.

Findings

Binary dark matter structure identified with Subaru imaging.

Mass estimates for subclusters and total cluster mass provided.

Simulations suggest a 3:1 off-axis merger explains relics and halo separation.

Abstract

The galaxy cluster PSZ2 G181.06+48.47 ($z=0.234$) is a post-merging system that exhibits symmetric double radio relics separated by ~2.7 Mpc. We present the first weak-lensing analysis of PSZ2 G181.06+48.47 and propose possible merging scenarios using numerical simulations. Our analysis with Subaru Hyper Suprime-Cam imaging identifies a binary dark matter structure consisting of northern and southern components, separated by ~500 kpc. Assuming Navarro-Frenk-White (NFW) halos, the masses for the northern and southern subclusters are $M_{200c}^{N} = 0.88_{-0.30}^{+0.35} \times 10^{14} M_{\odot}$ and $M_{200c}^{S} = 2.71_{-0.48}^{+0.51} \times 10^{14} M_{\odot}$, respectively. By superposing the two NFW halos, we determine the total mass of the cluster to be $M_{200c} = 4.22_{-1.00}^{+1.10} \times 10^{14} M_{\odot}$ ($M_{500c} = 2.90_{-0.69}^{+0.75} \times 10^{14} M_{\odot}$). Our mass estimate suggests that the two relics are located around the cluster $R_{200c}$, where the density of the intracluster medium is very low. Our idealized simulations find that an off-axis collision of a 3:1 major merger can simultaneously reproduce the observed relic and dark matter halo separations. From these findings, we suggest that the system is observed ~0.9 Gyr after the first pericenter passage and is returning from the first apocenter.