Mathematics – Logic
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004phdt.........6a&link_type=abstract
Thesis (PhD). PRINCETON UNIVERSITY, Source DAI-B 65/06, p. 2967, Dec 2004, 148 pages.
Mathematics
Logic
1
Scientific paper
There is now overwhelming evidence that only less than one percent of the mass in the universe can be observed via its optical signature. This thesis examines some of the signatures of (optically) invisible components of our universe, which comprise more than 99 percent of its energy content, namely dark energy (˜70%), dark matter (˜25%), and hot gas (˜4%). We start by introducing an alternative model for Cold Dark Matter (CDM), which consists of massive Primordial Black Holes (PBH's). We study the imprint of Poisson fluctuations, due to the discrete nature of PBH's, on the cosmological power spectrum. Combining our results with Ly-α forest observations, we arrive at a new upper limit on the mass of PBH's. We then point out that evaporation of haloes with a small of number of PBH's puts a lower cut-off on the mass of CDM haloes. The Wilkinson Microwave Anisotropy Probe (WMAP) has recently provided us with an all-sky map of Cosmic Microwave Background (CMB) with a resolution of ˜0.5°. The rest of the thesis is devoted to techniques that can be used to extract signatures of dark energy and hot gas from WMAP CMB maps. We first cross- correlate the WMAP maps with the distribution of galaxies in the Two Micron All Sky Survey (2MASS), and demonstrate the presence of Integrated Sachs-Wolfe (ISW) and thermal Sunyaev-Zel'dovich (SZ) effects at large and small angles respectively. In a flat universe, the ISW effect is interpreted as a signature of late time acceleration of the universe, caused by dark energy, while the thermal SZ effect traces the distribution of hot gas in clusters of galaxies. We go on to consider different aspects of observing dark energy via cross- correlating the CMB sky with galaxy surveys, and describe the potential of the method for constraining cosmological parameters. Finally, we devise an optimized filter match method to study the thermal SZ signature of 100 low- redshift X-ray clusters. Applying this method to the WMAP maps, we can put novel constraints on the gas fraction and concentration parameter of the Intra-Cluster Medium (ICM) in these clusters.
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