Anisotropic Thermal Conduction and the Cooling Flow Problem in Galaxy Clusters - Astrophysics > Cosmology and Nongalactic AstrophysicsReportar como inadecuado




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Abstract: We examine the long-standing cooling flow problem in galaxy clusters with 3DMHD simulations of isolated clusters including radiative cooling andanisotropic thermal conduction along magnetic field lines. The central regionsof the intracluster medium ICM can have cooling timescales of ~200 Myr orshorter-in order to prevent a cooling catastrophe the ICM must be heated bysome mechanism such as AGN feedback or thermal conduction from the thermalreservoir at large radii. The cores of galaxy clusters are linearly unstable tothe heat-flux-driven buoyancy instability HBI, which significantly changesthe thermodynamics of the cluster core. The HBI is a convective,buoyancy-driven instability that rearranges the magnetic field to bepreferentially perpendicular to the temperature gradient. For a wide range ofparameters, our simulations demonstrate that in the presence of the HBI, theeffective radial thermal conductivity is reduced to less than 10% of the fullSpitzer conductivity. With this suppression of conductive heating, the coolingcatastrophe occurs on a timescale comparable to the central cooling time of thecluster. Thermal conduction alone is thus unlikely to stabilize clusters withlow central entropies and short central cooling timescales. High centralentropy clusters have sufficiently long cooling times that conduction can helpstave off the cooling catastrophe for cosmologically interesting timescales.



Autor: Ian J. Parrish, Eliot Quataert, Prateek Sharma

Fuente: https://arxiv.org/







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