The galaxy cluster RX J0603.3+4214 at z = 0.225 is one of the rarest clusters boasting an extremely large ( \raise 0.817 pt \hbox { $ \scriptstyle \sim$ } 2 Mpc ) radio relic .
Because of the remarkable morphology of the relic , the cluster is nicknamed the “ Toothbrush Cluster ” .
Although the cluster ’ s underlying mass distribution is one of the critical pieces of information needed to reconstruct the merger scenario responsible for the puzzling radio relic morphology , its proximity to the Galactic plane b \sim 10 \arcdeg has imposed significant observational challenges .
We present a high-resolution weak-lensing study of the cluster with Subaru/Suprime Cam and Hubble Space Telescope imaging data .
Our mass reconstruction reveals that the cluster is composed of complicated dark matter substructures closely tracing the galaxy distribution , in contrast , however , with the relatively simple binary X-ray morphology .
Nevertheless , we find that the cluster mass is still dominated by the two most massive clumps aligned north-south with a \scriptstyle \sim 3:1 mass ratio ( M _ { 200 } = 6.29 _ { -1.62 } ^ { +2.24 } \times 10 ^ { 14 } M _ { \sun } and 1.98 _ { -0.74 } ^ { +1.24 } \times 10 ^ { 14 } M _ { \sun } for the northern and southern clumps , respectively ) .
The southern mass peak is \raise 0.817 pt \hbox { $ \scriptstyle \sim$ } 2 \arcmin offset toward the south with respect to the corresponding X-ray peak , which has a “ bullet ” -like morphology pointing south .
Comparison of the current weak-lensing result with the X-ray , galaxy , and radio relic suggests that perhaps the dominant mechanism responsible for the observed relic may be a high-speed collision of the two most massive subclusters , although the peculiarity of the morphology necessitates involvement of additional subclusters .
Careful numerical simulations should follow in order to obtain more complete understanding of the merger scenario utilizing all existing observations .