Astronomy and Astrophysics – Astrophysics
Scientific paper
Feb 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010head...11.3107r&link_type=abstract
American Astronomical Society, HEAD meeting #11, #31.07; Bulletin of the American Astronomical Society, Vol. 41, p.703
Astronomy and Astrophysics
Astrophysics
Scientific paper
Leading mechanisms invoked to explain the overcooling problem in galaxy clusters generally involve AGN heating, thermal conduction or (gas)dynamical friction. I will touch upon each of these processes but I will focus on the role of thermal conduction and turbulence driven by galaxy motions. In cool core clusters the heat buoyancy instability leads to B-fields ordered preferentially in the direction perpendicular to that of gravity, which significantly reduces the level of conduction below the classical Spitzer-Braginskii value. However, Chandra and XMM observations show that the cluster gas is rarely in perfect hydrostatic equilibrium. Sloshing motions due to minor mergers, AGN, or galaxy motions can significantly perturb the gas which may affect the level of conduction. We perform 3D AMR MHD simulations of the effect of turbulence driven by galaxy motions on the properties of the anisotropic thermal conduction. We show that subsonic motions, well within observational constraints, can randomize the magnetic field and essentially restore the conductive heat flow to the cool core to the level comparable to the theoretical maximum. Runs with radiative cooling show that the cooling catastrophe can be averted and the cluster core stabilized. We also quantify the amount of magnetic field amplification. Our results can be tested with future radio polarization measurements, and have implications for efficient metal dispersal in clusters.
Oh Siang Peng
Ruszkowski Mateusz
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