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T. J. Dennis, B. D. G. Chandran (University of Iowa)
The radiative cooling time at the centers of many galaxy clusters is much shorter than a typical cluster's age, yet recent x-ray observations of a number of clusters show that very little intracluster plasma cools to temperatures below roughly one-third of a cluster's average temperature. Some heating mechanism must offset radiative cooling in cluster cores to explain these observations. In this poster, we describe our recent results on plasma heating from turbulent intracluster motions. We fit density and temperature data for three clusters with analytic profiles, and calculate the turbulent velocity profiles needed in order for radiative cooling to be balanced by turbulent diffusion of heat, viscous dissipation of turbulent motions, and thermal conduction. We set the dominant eddy length scale (L) equal to a small value (0.5 kpc) plus a free constant times the radius. We also include the effects of buoyancy forces, which in the absence of nonthermal pressure inhibit turbulent diffusion when the eddy turnover rate is less than roughly the Brunt-Väisälä frequency. We find velocities in the range 100-300 km/s, depending on radius, and quantify the relative importance of dissipation and turbulent diffusion as a function of L. This work was supported by NSF grant AST-0098086 and DOE grants DE-FG02-01ER54658 and DE-FC02-01ER54651 at the University of Iowa.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.