Internal Velocity and Mass Distributions in Clusters of Galaxies for a Variety of Cosmogonic Models

The mass and velocity distributions in the outskirts ($0.5-3.0h^{-1}$Mpc) of clusters of galaxies are examined for a suite of cosmogonic models utilizing large-scale Particle-Mesh (PM) simulations ($500^3$ cells, $250^3$ particles and box size of $100h^{-1}$Mpc, giving a nominal resolution of $0.2h^{-1}$Mpc with the true resolution about $0.5h^{-1}$Mpc). Through a series of model computations, designed to isolate the different effects, we find that both $\Omega_0$ and $P_k$ ($\lambda\le 16h^{-1}$Mpc) are important to the mass and velocity distributions in clusters of galaxies. More details in the full abstract.Comment: 29p plaintex submitted to The Astrophysical Journal on Jan 7, 199

The Intergalactic Medium and Soft X-ray Background

I present an overview of some of the recent advances in our understanding of the distribution and evolution of the ordinary, baryonic matter in the universe. Two observations that strongly suggest that most of the baryons seen at high redshift ($z\ge 2$) have turned into some forms yet undetected at $z=0$ are highlighted. With the aid of large-scale cosmological hydrodynamic simulations, it is shown that most of the baryons today are in a gaseous form with a temperature of $10^5-10^7~$Kelvin -- the "warm/hot gas", shock heated during the gravitational collapse and formation of the large-scale structure at low redshift. Primarily line emissions from this warm/hot gas may account for a large fraction of the residual (after removal of identifiable discrete sources) soft X-ray background at $h\nu < 1.0$keV. How this warm/hot gas may be detected by the next generation of EUV and soft X-ray instruments is indicated. Detection or non-detection of this warm/hot gas will have profound implications for cosmology.Comment: An invited overview presented at "Small Missions for Energetic Astrophysics", Los Alamos, March 1999, full paper with color figures can be obtained at http://astro.princeton.edu/~cen/PROJECTS/p1/p1.htm