Large-scale structure and dynamics of the most X-ray luminous galaxy cluster known – RX J1347−1145

We present photometric, spectroscopic and weak lensing analysis of the large-scale structure and dynamics of the most X-ray luminous galaxy clusterknown, RX J1347−1145, at z = 0.451. We spectroscopically confirmed 47 new members with Low Dispersion Survey Spectrograph 3 (LDSS3) on the Magellan telescope. Together with previously known members, we measure a new velocity dispersionof 1163 ± 97 km s −1 . The mass inferred from our velocity dispersionis M 200 = 1.16 +0.32 −0.27 × 10 15 M� , with r 200 = 1.85 Mpc, under the assumption of a singular isothermal sphere. We also present a weak lensing analysis using deep Canada–France–Hawaii Telescope (CFHT) data on this cluster, and find a deprojected mass of 1.47 +0.46 −0.43 × 10 15 M� withinr200, in excellent agreement with our dynamical estimate. Thus, our new dynamical mass estimate is consistent with that from weak lensing and X-ray studies in the literature, resolving a previously claimed discrepancy. We photometrically detect and spectroscopically confirm another massive cluster with σ = 780 ± 100 km s −1 and M 200 = 3.4 +1.4 −1.1 × 10 14 M� ∼ 7M pc south-west of RX J1347−1145, which we refer to as RXJ1347−SW. Our spectroscopic survey reveals a possible excess of galaxies in velocity space in the region between RX J1347−1145 and RXJ1347−SW; comparing with simulations, this excess appears consistent with that expected from a large filamentary structure traced by galaxies connecting these two clusters.