Chandra Observations of the Spectacular A3411-12 Merger Event

Andrade-Santos, Felipe and Weeren, Reinout J. van and Gennaro, Gabriella Di and Wittman, David and Ryu, Dongsu and Lal, Dharam Vir and Placco, Vinicius M. and Fogarty, Kevin and Jee, M. James and Stroe, Andra and Sobral, David and Forman, William R. and Jones, Christine and Kraft, Ralph P. and Murray, Stephen S. and Brüggen, Marcus and Kang, Hyesung and Santucci, Rafael and Golovich, Nathan and Dawson, William (2019) Chandra Observations of the Spectacular A3411-12 Merger Event. The Astrophysical Journal, 887 (1): 31. ISSN 0004-637X

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Abstract

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.