Hubble Space Telescope and Hyper-Suprime-Cam Weak-lensing Study of the Equal-mass Dissociative Merger CIZA J0107.7+5408

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 Navarro–Frenk–White halos to the lensing signal, we find an equal-mass merger with subcluster masses of M 200 , NE = 2.8 − 1.1 + 1.1 × 10 14 M ⊙ and M 200 , SW = 3.1 − 1.2 + 1.2 × 10 14 M ⊙ . Moreover, the mass-to-light ratios of the subclusters, ( M / L ) NE = 571 − 91 + 89 M ☉ / L ☉ , B and ( M / L ) SW = 564 − 89 + 87 M ☉ / L ☉ , B , are found to be consistent with each other and within the range of mass-to-light ratios found for galaxy clusters.