Gravitational Evolution of LargeScale Structure in the Universe.
Abstract
We study large scale properties of the universe under a popular hypothesis that the large scale structure has evolved from primordial Gaussian random fluctuations by gravitational instability. For this purpose we have developed a highly efficient ParticleMesh Nbody code. Large simulations with a reasonable prescription for galaxy formation have shown that the biased Cold Dark Matter (CDM) model is quite successful in describing the observed large scale distribution and motions of galaxies. We have found that nonlinear gravitational evolution increases the zero crossing scale of the correlation function. The clustercluster correlation function (xi _{cc}) from 5 large CDM simulations shows on average a lower amplitude than some observational claims. Since the observational xi_ {cc} is controversial, a deep 3D cluster survey with an objective cluster selection criterion is required. The supercluster correlation function calculated from these CDM simulations is consistent with observations. The three dimensional morphology of large scale structure in our CDM simulations can be described as filamentary structure embedded in diffuse walls and beaded with dense clusters. The slight meatball topology in the biased CDM model has been explained as due to the nonlinear coupling of statistical biasing and gravitational evolution. This shift, which also exists in observed samples, reaches a maximum for moderate bias in the CDM model (b ~ 2) and might be evidence for the existence of biasing in the distribution of galaxies. We present a new technique of Nbody simulation in a box with nonequal sides, which allows us to simulate the universe over very large scales. A long rod simulation is made to simulate a recent pencil beam survey and a detailed statistical hypothesis test is made. We simulate future surveys of large scale structure like the CfA century survey, the million galaxy survey, and peculiar velocity field surveys. We find that 100 h^{1} Mpc scale structures and peculiar velocity flows are easily found in our CDM model which has relatively small power at such scales and that in unbiased models like the Hot Dark Matter model it is difficult to find voids as empty as those in the observations.
 Publication:

Ph.D. Thesis
 Pub Date:
 1991
 Bibcode:
 1991PhDT.........1P
 Keywords:

 Physics: Astronomy and Astrophysics;
 Astronomical Models;
 Dark Matter;
 Galactic Clusters;
 Galactic Evolution;
 Galaxies;
 Gravitation;
 Many Body Problem;
 Simulation;
 Universe;
 Bias;
 Correlation;
 Hypotheses;
 Nonlinearity;
 Pencil Beams;
 Roots Of Equations;
 Statistical Tests;
 Surveys;
 Astrophysics