Chandra Observations of the Spectacular A3411-12 Merger Event
  We present deep Chandra observations of A3411-12, a remarkable merging
cluster that hosts the most compelling evidence for electron re-acceleration at
cluster shocks to date. Using the $Y_X-M$ scaling relation, we find $r_{500}
\sim 1.3$ Mpc, $M_{500} = (7.1 \pm 0.7) \times 10^{14} \ M_{\rm{\odot}}$,
$kT=6.5\pm 0.1$ keV, and a gas mass of $M_{\rm g,500} = (9.7 \pm 0.1) \times
10^{13} M_\odot$. The gas mass fraction within $r_{500}$ is $f_{\rm g} = 0.14
\pm 0.01$. We compute the shock strength using density jumps to conclude that
the Mach number of the merging subcluster is small ($M \leq
1.15_{-0.09}^{+0.14}$). We also present pseudo-density, projected 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.
