University of Minnesota
School of Physics & Astronomy

Physics and Astronomy Calendar

Monday, December 12th 2016
12:15 pm:
Speaker: Tom Jones (University of Minnesota)
Subject: The Dynamics of Galaxy Cluster Formation as Revealed by Cluster Baryons

Galaxy clusters are the most massive bound systems in the universe and the last stage of hierarchical structure formation. They occupy intersections of cosmic filaments, where they come together through accretion from the filaments and incredibly violent mergers with other clusters. While dark matter accounts for about 85% of cluster total mass, ~ 90% of the remaining, baryonic matter is in the form of diffuse, keV temperature plasma, known as the "intracluster medium" or ICM. Being dissipative on "small" scales, ICM plasma captures important characteristics of cluster formation dynamics that are otherwise obscure. At the lowest order, an ICM is virialized and relaxes to a hydrostatic equilibrium with the cluster's gravitational potential. But the cluster formation process is unsteady, non-symmetric and subject to frequent external gravitational distortion, so, at the next level ICMs are expected to be crossed with transonic winds, gravity waves, concentrated, infalling streams, weak to moderate strength shocks and turbulence, all of whose distributions should reveal much about the cluster history and its environment. The links between these patterns and cluster formation are especially strong outside of the central cores of the clusters, where thermal emissions are weak, but where non-thermal processes can be strong enough to provide discriminating signatures of ICM dynamics. I will review these issues, including some current puzzles, focusing on our local simulation and modeling efforts, past, current and planned.

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