BUOYANT BUBBLES IN INTRACLUSTER GAS: EFFECTS OF MAGNETIC FIELDS AND ANISOTROPIC VISCOSITY

Recent observations by Chandra and XMM-Newton indicate that there are complex structures at the cores of galaxy clusters, such as cavities and filaments. One plausible model for the formation of such structures is the interaction of radio jets with the intracluster medium (ICM). To investigate this idea, we use three-dimensional magnetohydrodynamic simulations including anisotropic (Braginskii) viscosity to study the effect of magnetic fields on the evolution and morphology of buoyant bubbles in the ICM. We investigate a range of different initial magnetic field geometries and strengths, and study the resulting X-ray surface brightness distribution for comparison to observed clusters. Magnetic tension forces and viscous transport along field lines tend to suppress instabilities parallel, but not perpendicular, to field lines. Thus, the evolution of the bubble depends strongly on the initial field geometry. We find that toroidal field loops initially confined to the interior of the bubble are best able to reproduce the observed cavity structures.

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