A Database of Cobe-normalized Cdm Simulations (abbreviated Version)

We have simulated the formation and evolution of large-scale structure in the universe, for 68 different COBE-normalized cosmological models. For each cosmological model, we have performed between 1 and 3 simulations, for a total of 160 simulations. This constitutes the largest database of cosmological simulations ever assembled, and the largest cosmological parameter space ever covered by such simulations. We are making this database available to the astronomical community. We provide instructions for accessing the database and for converting the data from computational units to physical units. The database includes Tilted Cold Dark Matter (TCDM) models, Tilted Open Cold Dark Matter (TOCDM) models, and Tilted Λ Cold Dark Matter (TΛCDM) models. (For several simulations, the primordial exponent n of the power spectrum is near unity, hence these simulations can be considered as “untilted.”) The simulations cover a 4-dimensional cosmological parameter phase space, the parameters being the present density parameter Ω0, cosmological constant λ0, and Hubble constant H0, and the rms density fluctuation σ8 at scale 8h Mpc. All simulations were performed using a PM algorithm with 64 particles on a 128 mesh, in a cubic volume of comoving size 128 Mpc. Each simulation starts at a redshift of 24, and is carried up to the present. More simulations will be added to the database in the future. We have performed a limited amount of data reduction and analysis of the final states of the simulations. We computed the rms density fluctuation, the 2-point correlation function, the velocity moments, and the properties of clusters. The details of these calculations are presented in the full version of this paper. In this abbreviated version, we present only the analysis of the rms density fluctuation and two-point correlation function. Our results are the following: (1) The numerical value σ 8 of the rms density fluctuation differs from the value σ cont 8 obtained by integrating the power spectrum at early times and extrapolating linearly up the the present. This results from the combined effects of discreteness in the numerical representation of the power spectrum, the presence of a Gaussian factor in the initial conditions, and late-time nonlinear evolution. The first of these three effects is negligible. The second and third are Department of Astronomy, University of Texas, Austin, TX 78712 Center for Relativity, University of Texas, Austin, TX 78712 Department of Physics, University of Texas, Austin, TX 78712