2019ApJ...887...31A

We present deep Chandra observations of A3411-12, a remarkable merging cluster that hosts the most compelling evidence for electron reacceleration at cluster shocks to date. Using the Y_X–M scaling relation, we find r₅₀₀ ∼ 1.3 Mpc, M₅₀₀=(7.1±0.7)×10¹⁴ M_☉, kT=6.5±0.1keV, and a gas mass of M_g,500=(9.7±0.1)×10¹³M_☉. The gas mass fraction within r₅₀₀ is f_g=0.14±0.01. We compute the shock strength using density jumps to conclude that the Mach number of the merging subcluster is small (M≤ 1.15_–0.09^+0.14). We also present density, temperature, pseudo-pressure, and pseudo-entropy maps. Based on the pseudo-entropy map, we conclude that the cluster is undergoing a mild merger, consistent with the small Mach number. On the other hand, radio relics extend over Mpc scale in the A3411-12 system, which strongly suggests that a population of energetic electrons already existed over extended regions of the cluster.