We report the discovery of a binary galaxy cluster merger via a search of the
redMaPPer optical cluster catalog, with a projected separation of 535 kpc
between the BCGs. Archival XMM-Newton spectro-imaging reveals a gas peak
between the BCGs, suggesting a recent pericenter passage. We conduct a galaxy
redshift survey to quantify the line-of-sight velocity difference (153±281
km/s) between the two subclusters. We present weak lensing mass maps from
archival HST/ACS imaging, revealing masses of M200​=4.5±0.8×1014
and 2.8±0.7×1014 M⊙​ associated with the southern and
northern galaxy subclusters respectively. We also present deep GMRT 650 MHz
data revealing extended emission, 420 kpc long, which may be an AGN tail but is
potentially also a candidate radio relic. We draw from cosmological n-body
simulations to find analog systems, which imply that this system is observed
fairly soon (60-271 Myr) after pericenter, and that the subcluster separation
vector is within 22∘ of the plane of the sky, making it suitable for an
estimate of the dark matter scattering cross section. We find σDM​=1.1±0.6 cm2/g, suggesting that further study of this system could
support interestingly tight constraints.Comment: accepted to Ap