Exemplary Merging Clusters: Weak-lensing and X-ray Analysis of the
  Double Radio Relic Merging Galaxy Clusters MACS 1752.0+4440 and ZWCL
  1856.8+6616
  The investigation of merging galaxy clusters that exhibit radio relics is
strengthening our understanding of the formation and evolution of galaxy
clusters, the nature of dark matter, the intracluster medium, and astrophysical
particle acceleration. Each merging cluster provides only a single view of the
cluster formation process and the variety of merging clusters is vast. Clusters
hosting double radio relics are rare and extremely important because they allow
tight constraints on the merger scenario. We present a weak-lensing and X-ray
analysis of MACSJ1752.0+4440 ($z$=0.365) and ZWCL1856.8+6616 ($z$=0.304), two
double radio relic clusters. Our weak-lensing mass estimates show that each
cluster is a major merger with approximately 1:1 mass ratio. The total mass of
MACSJ1752.0+4440 (ZWCL1856.8+6616) is $M_{200}=14.7^{+3.8}_{-3.3}\times10^{14}\
$M$_\odot$ ($M_{200}=2.4^{+0.9}_{-0.7}\times10^{14}\ $M$_\odot$). We find that
these two clusters have comparable features in their weak-lensing and gas
distributions, even though the systems have vastly different total masses. From
the likeness of the X-ray morphologies and the remarkable symmetry of the radio
relics, we propose that both systems underwent nearly head-on collisions.
However, revelations from the hot-gas features and our multiwavelength data
analysis suggest that ZWCL1856.8+6618 is likely at a later merger phase than
MACSJ1752.0+4440. We postulate that the SW radio relic in MACSJ1752.0+4440 is a
result of particle re-acceleration.
