UC Davis

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 YX-M scaling relation, we find r 500 ∼ 1.3 Mpc, M500 =(7.1 ± 0.7) × 1014 M⊙, kT =6.5 ± 0.1 keV, and a gas mass of Mg,500 =(9.7 ± 0.1) × 1013 M⊙. The gas mass fraction within r 500 is fg = 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.