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 cluster
known, RX J1347-1145, at z=0.451. We spectroscopically confirmed 47 new members
with LDSS3 on the Magellan telescope. Together with previously known members,
we measure a new velocity dispersion of 1163(+/-97) km/s. The mass inferred
from our velocity dispersion is M200 = 1.16^{+0.32}_{-0.27}x10^{15} solar mass,
with r200=1.85Mpc, under the assumption of a singular isothermal sphere. We
also present a weak lensing analysis using deep CFHT data on this cluster, and
find a deprojected mass of 1.47^{+0.46}_{-0.43}x10^{15} solar mass 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
sigma=780(+/-100) km/s and M200=3.4^{+1.4}_{-1.1}x10^{14} solar mass ~7Mpc
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.
