Multi-wavelength Analysis of the Merging Galaxy Cluster A115
  A115 is a merging galaxy cluster at $z\sim0.2$ with a number of remarkable
features including a giant ($\sim2.5$ Mpc) radio relic, two asymmetric X-ray
peaks with trailing tails, and a peculiar line-of-sight velocity structure. We
present a multi-wavelength study of A115 using optical imaging data from
Subaru, X-ray data from $Chandra$, and spectroscopic data from the Keck/DEIMOS
and MMT/Hectospec instruments. Our weak-lensing analysis shows that the cluster
is comprised of two subclusters whose mass centroids are in excellent agreement
with the two BCG positions ($\lesssim10$"). By modeling A115 with a
superposition of two Navarro-Frenk-White halos, we determine the masses of the
northern and southern subclusters to be $M_{200}=1.58_{-0.49}^{+0.56}\times
10^{14} \text{M}_{\odot}$ and $3.15_{-0.71}^{+0.79}\times 10^{14}
\text{M}_{\odot}$, respectively. Combining the two halos, we estimate the total
cluster mass to be $M_{200}=6.41_{-1.04}^{+1.08}\times10^{14} \text{M}_{\odot}$
at $R_{200}=1.67_{-0.09}^{+0.10}$ Mpc. These weak-lensing masses are
significantly (a factor of 3-10) lower than what is implied by the X-ray and
optical spectroscopic data. We attribute the difference to the gravitational
and hydrodynamic disruption caused by the collision between the two
subclusters.
