Cosmological simulations show that dark matter halos contain a wealth of substructure. These subhalos are assumed have a mass distribution that extends down to the smallest mass in the Cold Dark Matter (CDM) hierarchy, which lies below the current resolution limit of simulations. Substructure has important ramifications for indirect dark matter detection experiments as the signal depends sensitively on the small-scale density distribution of dark matter in the Galactic halo. A clumpy halo produces a stronger signal than halos where the density is a smooth function of radius.
However, the small-scale Universe presents a daunting challenge for models of structure formation. In the CDM paradigm, structures form in a hierarchical fashion, with small-scale perturbations collapsing first to form halos that then grow via mergers. However, near the bottom of the hierarchy, dark matter structures form nearly simultaneously across a wide range of scales.
To explore these small scales, I use a series of simulations of scale-free cosmological models, where the initial density power spectrum is a power-law. I can effectively examine various scales in the Universe by using the index in these artificial cosmologies as a proxy for scale. This approach is not new, but my simulations are larger than previous such simulations by a factor of 3 or more.
My results call into question the often made assumption that the subhalo population is scale-free. The subhalo population does depend on the mass of the host. By combining my study with others, I construct a phenomenological model for the subhalo mass function. This model shows that the full subhalo hierarchy does not greatly boost the dark matter annihilation flux of a host halo. Thus, the enhancement of the Galactic halo signature due to substructure can not alone account the observed flux of cosmic rays produced by annihilating dark matter.
Finally, I examine the nonlinear power spectrum, which is used to determine cosmological parameters based on large-scale, observational surveys. I find that in this nonlinear regime, my results are not consistent with currently used fitting formulae and present my own empirical formula. / Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2009-09-25 01:01:39.714
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OKQ.1974/5219 |
| Date | 26 September 2009 |
| Creators | ELAHI, PASCAL |
| Contributors | Queen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.)) |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Format | 4311735 bytes, application/pdf |
| Rights | This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner. |
| Relation | Canadian theses |
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