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Session 52 - Simulations of Clusters of Galaxies.
Display session, Tuesday, January 16
North Banquet Hall, Convention Center
We have developed an improved version of Smoothed Particle Hydrodynamics (SPH) -- Adaptive SPH (ASPH) -- for cosmological gas dynamical simulations. We have applied our ASPH method to two models -- Cold Dark Matter (CDM) and Mixed Hot-and-Cold Dark Matter (CHDM) -- to simulate large scale structure formation in 2D. We have analyzed these simulations to determine how the ratio of gas to total density in each differs from that of their universal mean values -- the density bias -- as a function of the degree of overdensity of the matter. Models like these with Ømega=1 and with Ømega_B limited by standard Big-Bang nucleosynthesis may be inconsistent with previous X-ray and optical determinations of the baryonic mass fraction in rich clusters. We discuss the velocity and temperature biases of gas and dark matter in clusters. We discuss the fitting of X-ray brightness profiles of clusters to measure cluster total mass and gas mass fraction, assuming clusters are isothermal spheres in hydrostatic equilibrium. The effect of merging and substructure on mass determination will also be discussed.
