A Weak-lensing and Near-infrared Study of A3192: Disassembling a Richness Class 3 Abell Cluster

We present a joint gravitational lensing and near-infrared study of the galaxy cluster Abell 3192 (A3192) that has been associated both with galaxies at z = 0.168 and with the X-ray luminous cluster RXC J0358.8-2955 (RXC J0358) at z = 0.425. Weak-lensing analysis of our Hubble Space Telescope snapshot observation with the Advanced Camera for Surveys detects two mass over-densities separated by ~2 arcmin, one adjacent to the optical position of A3192 (4.4σ significance) and the other adjacent to the X-ray position of RXC J0358 (6.2σ significance). These mass peaks coincide with peaks in the K-band luminosity density of galaxies with near-infrared colors consistent with the red sequence at z = 0.168 and z = 0.425, respectively. Moreover, the Bayesian evidence of parameterized mass models that include two cluster/group-scale halos centered on the respective mass peaks exceeds that of single-halo models by a factor of >=10. The total projected mass of each galaxy system within 250 kpc of the respective peaks is M _WL(z = 0.168) ~= 3 × 10¹³ M _⊙ and M _WL(z = 0.425) ~= 1.2 × 10¹⁴ M _⊙, both with total mass-to-light ratios of M _WL/L_K ~= 20 M _⊙/L _⊙. The original Abell cluster therefore comprises two independent galaxy systems—a foreground group at z = 0.168 and RXC J0358 at z = 0.425. Our results demonstrate the power of combining X-ray, near-infrared, and weak-lensing observations to select massive clusters, place those clusters and interloper galaxy systems along the line of sight, and measure their masses. This combination will be invaluable to robust interpretation of future high-redshift cluster surveys, including eROSITA.