2025ApJ...984...26A

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 (DM) 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 ${M}_{200c}^{\,\rm{N}\,}=0.8{8}_{-0.30}^{+0.35}\times 1{0}^{14}{M}_{\odot }$ and ${M}_{200c}^{\,\rm{S}\,}=2.7{1}_{-0.48}^{+0.51}\times 1{0}^{14}{M}_{\odot }$, respectively. By superposing the two NFW halos, we determine the total mass of the cluster to be ${M}_{200c}=4.2{2}_{-1.00}^{+1.10}\times 1{0}^{14}{M}_{\odot }$(${M}_{500c}=2.9{0}_{-0.69}^{+0.75}\times 1{0}^{14}{M}_{\odot }$). 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 DM 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.