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

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.