Abstract:
The nonlinear growth of a self gravitating collisionless cosmic system consisting of 32768 particles has been studied under two different initial conditions. Each particle having a mass equal to 2x1012 Mq (Mq =Solar Mass) thus corresponds to the mass of an Andromeda sized galaxy. The initial conditions are generated using Zel’dovich’s formulation with (a) a Poisson distribution and (b) a Harrison-Zel’dovich power spectrum, on a scale of 60 Mpc in present units. An W =1 universe is assumed in both the models. The simulation starts at z=4 and the evolution is followed until an expansion by a factor of 5 to identify the simulated system with the present universe. Particle-Particle/Particle-Mesh code for the integration of the equations of motion is employed using a 643 mesh with triply periodic boundary conditions. The results of these computations are analyzed in terms of the two point correlation functions, the mean relative peculiar velocities between particle pairs and the ms peculiar relative velocities of pairs in the radial 1/2 and the tangential 1/2 directions. The main conclusion is that the white noise initial conditions produce a clustering level at late stages of evolution which is very close to the observed galaxy-galaxy correlation g =1.8 in the relation S® = (r/ro)-y , while the power spectrum with n = -1 produces a very highly clustered distribution which does not explain observation. However, this final conclusion may be a result of the choice of the variance in the Gaussain distribution of amplitudes to generate the initial conditions. Further investigations in this matter are warranted.
Page(s):
37-47
DOI:
DOI not available
Published:
Journal: Proceedings of Pakistan Academy of Sciences, Volume: 33, Issue: 1--2, Year: 1996