MC2: Subaru and Hubble Space Telescope Weak-lensing Analysis of the Double Radio Relic Galaxy Cluster PLCK G287.0+32.9

The second most significant detection of the Planck Sunyaev-Zel’dovich survey, PLCK G287.0+32.9 (z = 0.385), boasts two similarly bright radio relics and a radio halo. One radio relic is located ∼ 400 {kpc} NW of the X-ray peak and the other ∼ 2.8 Mpc to the SE. This large difference suggests that a complex merging scenario is required. A key missing puzzle for the merging scenario reconstruction is the underlying dark matter distribution in high resolution. We present a joint Subaru Telescope and Hubble Space Telescope weak-lensing analysis of the cluster. Our analysis shows that the mass distribution features four significant substructures. Of the substructures, a primary cluster of mass {M}_200{{c}}={1.59}_-0.22^+0.25× {10}¹⁵ {h}₇₀^-1 {M}_⊙ dominates the weak-lensing signal. This cluster is likely to be undergoing a merger with one (or more) subcluster whose mass is approximately a factor of 10 lower. One candidate is the subcluster of mass {M}_200{{c}}={1.16}_-0.13^+0.15× {10}¹⁴ {h}₇₀^-1 {M}_⊙ located ∼ 400 {kpc} to the SE. The location of this subcluster suggests that its interaction with the primary cluster could be the source of the NW radio relic. Another subcluster is detected ∼ 2 Mpc to the SE of the X-ray peak with mass {M}_200{{c}}={1.68}_-0.20^+0.22× {10}¹⁴ {h}₇₀^-1 {M}_⊙ . This SE subcluster is in the vicinity of the SE radio relic and may have created the SE radio relic during a past merger with the primary cluster. The fourth subcluster, {M}_200{{c}}={1.87}_-0.22^+0.24× {10}¹⁴ {h}₇₀^-1 {M}_⊙ , is NW of the X-ray peak and beyond the NW radio relic.