Adventures in numerical cosmology.

摘要

This topic of this dissertation is the use of numerical simulations in the study of cosmological structure formation. It is split into two parts. The first part (Chapters 2-4) deals with collisionless dark matter simulations, the second part (Chapters 5-7) with hydrodynamic simulations. In both parts I first present a detailed overview of the relevant numerical techniques, and proceed to present results of several distinct investigations that were greatly aided by numerical simulations.; In Chapter 3 I discuss the influence of varying the nature of a type of dark energy on the properties of galaxy and galaxy-group size dark matter halos. Using a suite of 5 N-body simulations, I show how the mass function and concentration-mass relation depends on the value of w, the dark energy equation of state parameter. These results show that existing analytical models can successfully be extended to models with dark energy different than a plain cosmological constant. Comparisons with observational data from galaxy rotation curves allows us to put constraints on w, and we find that models with w > -1 and high sigma 8 are significantly disfavored.; In Chapter 4 I discuss recent simulations of the formation of the earliest, and thus least massive, supersymmetric dark matter halos in the universe. At the mass scales of interest, ∼10-6--10-2 M⊙ , nearly simultaneous, not hierarchical as it does for larger masses. As a result early substructure has a much lower density contrast compared to its host halo. The relative abundance of dark matter substructure, however, is not affected, and we show that it follows the same self-similar scaling law found for the substructure of present day galaxy cluster dark matter halos.; In Chapter 6 I present a study of the environmental impact of the first active galactic nuclei that may have formed ∼150 Myr after the big bang in low-mass minihalos. Accreting black holes in the 100--1000 M⊙ mass range may be the natural remnants of the first generation of stars.; Finally, in Chapter 7, I conclude with a little follow-up to the previous miniquasar simulations. The fact that the environment of an early miniquasar is strongly heated, yet remains mostly neutral, has interesting consequences for the predicted 21cm signal emitted by the hot diffuse neutral gas. (Abstract shortened by UMI.)