Computer Science
Scientific paper
Aug 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992phdt.........5b&link_type=abstract
Ph.D. Thesis Ohio State Univ., Columbus.
Computer Science
Computerized Simulation, Dark Matter, Galaxies, Halos, Universe, Interstellar Matter, Many Body Problem, Mass Distribution, Velocity Distribution
Scientific paper
Using N-body simulations in which large dynamic ranges in mass and length can be achieved simultaneously, the mass function, spatial correlation properties, and peculiar velocity field of dark matter galaxy halos were investigated as a function of environment. A standard cold dark matter (CDM) universe was assumed. Halos were identified using a friends-of-friends algorithm with linking parameters l = .1, 0.2 and 0.3. The mass function of l = 0.2 and 0.3 halos is well-fit by a power law of index -1 plus or minus 0.1 for 1010 M(solar) approximately less than M(halo) approximately less than 1013 M(solar). The mass function of l = 0.1 halos is well-fit by a power law of index approximately -1.1 to approximately -1.4. The Press-Schecter prediction is a poor fit to the numerical mass function. Below a mass scale of approximately 1011 to approximately 1012 M(solar), l = 0.2 halos are produced with the same efficiency in regions of high, low, and average background mass density. The formation of halos with M(halo) approximately greater than 1013 M(solar) is strongly biased toward regions of high mass density. From the two-point correlation function, xi(r), the linear bias model is a good description of the formation of l = 0.2 halos (on scales up to approximately 30h-1 Mpc, but not the l = 0.1 and 0.3 halos. In a low normalization universe (1/sigma 8 = 2.5), high mass halos are more strongly clustered than low mass halos; in a high normalization universe (1/sigma 8 = 1.5), high and low mass halos are clustered to the same degree. All the power in xi(r) for l = 0.1 halos comes from halos in high density regions, and for the l = 0.2 and 0.3 halos, most of the power in xi(r) comes from halos in high density regions, but there is a contribution from halos in average density regions. High mass l = 0.2 and 0.3 halos are fair tracers of the major mass motions in the simulation, and their low mass counterparts are biased tracers. The larger the local background density, the larger is upsilon(rms) of the halos, but it is not straightforward to estimate a local suppression or enhancement in mass density from upsilon(rms). For 2.5h-1 Mpc approximately less than r approximately less than 12.6h-1 Mpc, the velocity correlation function for l = 0.2 halos at 1/sigma 8 = 0.2 agrees well with the velocity correlation function of spiral galaxies.
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