AGN-driven convection in clusters of galaxies

This poster shows how magnetic fields and cosmic rays affect the convective stability criterion of the intracluster medium (ICM). The poster also suggests that clusters are convective and presents a two-fluid (plasma and cosmic-ray) mixing-length model of galaxy clusters that accounts for convection driven by the cosmic rays produced by a central radio source. The model compares reasonably well with observational data. The model also predicts levels of diffuse gamma-ray emission resulting from interactions between cosmic-ray protons and thermal nucleons that will be detectable by GLAST. Convection may be important for solving the cooling-flow problem and regulating the temperature and density structure of the ICM, thereby affecting the mass-observable relations needed to use cluster surveys to constrain cosmological parameters. This work was supported by NASA under ATP grant NNG 05GH39G and by NSF under grant AST 05-49577.