Chandra Observations of the Spectacular A3411–12 Merger Event

Abstract

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±0.1 keV, and a gas mass of M_g,₅₀₀ = (9.7±0.1)×10¹³ M_⊙. 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+^(0.14)_(−0.09)). 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.

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