| Abstract
| - We present photometric, spectroscopic and weak lensing analysis of the large-scale structure and dynamics of the most X-ray luminous galaxy cluster known, 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 dispersion of 1163 ± 97 km s−1. The mass inferred from our velocity dispersion is M200= 1.16+0.32−0.27× 1015 M⊙, with r200= 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× 1015 M⊙ within r200, 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 M200= 3.4+1.4−1.1× 1014 M⊙∼ 7 Mpc 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.
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