AAS 199th meeting, Washington, DC, January 2002
Session 69. Clusters of Galaxies - I
Oral, Tuesday, January 8, 2002, 10:00-11:30am, Jefferson West

## [69.06] A New Picture of Galaxy Cluster Cooling Cores: Formation via Hierarchical Mergers

P.M. Motl, J.O. Burns (University of Missouri - Columbia), C. Loken (CITA), M.L. Norman (UCSD), G. Bryan (University of Oxford)

New state of the art large-scale structure simulations have suggested a novel scenario for the formation of cooling cores in rich clusters. We find that cores of cool gas, material that would be identified as a classical cooling flow based upon its X-Ray luminosity excess and temperature profile, are built from the accretion of discrete, stable subclusters. Any cooling flow'' present is overwhelmed by the velocity field within the cluster. Thus, the inclusion of consistent initial cosmological conditions for the cluster within its surrounding environment is crucial when attempting to address the evolution of cooling cores in rich galaxy clusters. This new model for the hierarchical assembly of cooling cores naturally explains the high frequency of these cores in rich galaxy clusters despite the fact that a majority of rich clusters also show evidence of substructure which is believed to arise from recent merger activity. Also, complex filamentary structures of cool gas in our simulations appear similar to those seen in recent Chandra observations. Our simulations were computed with a coupled N-body, Eulerian AMR hydrodynamics cosmology code that properly treats the effects of radiative cooling by the gas. We employ seven levels of refinement to attain a peak resolution of 15.6 \mathrm{h}-1 kpc within a volume 256 \mathrm{h}-1 Mpc on a side and assume a standard \LambdaCDM cosmology.