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Title: Application of novel analysis techniques to cosmic microwave background astronomy
Author: Jones, A. W.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1998
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The data from Cosmic Microwave Background (CMB) experiments are becoming more complex with each new experiment. A consistent way of analysing these data sets is required so that direct comparison is possible between the various experimental results. This thesis presents several techniques that can be used to analyse CMB data. A summary of the processes involved in the formation of the fluctuations and the resultant radiation we expect to see in our sky maps is presented. This includes both the CMB and other emission components that operate at the frequencies covered by CMB experiments. These other components are the Sunyaev-Zel'dovich effect, point source emissions and various Galactic foregrounds (namely dust, bremsstrahlung and synchrotron emission). Various present and future experiments are discussed. Preliminary analysis is done on existing data taken from the Tenerife and Jodrell Bank experiments. This data is used to put constraints on Galactic emissions and point source contributions. The data discussed covers the 5 GHz to 33 GHz frequency range which is at the lower end of the useful CMB spectral window. Lower frequency surveys are used to put constraints on the spectral index of some of the Galactic foregrounds (the frequency range is not large enough to put constraints on dust emission which is expected to dominate at higher frequencies). The Tenerife experiments are used to put constraints on the level of the CMB anisotropy. Maximum Entropy Methods (MEM), the Wiener filter, CLEAN and Singular Value Decomposition are introduced. These four methods offer different alternatives to find the best underlying cosmological signal within the noisy data. The usual approach of a positive-only Maximum entropy is enlarged to cover both positive and negative fluctuations, as well as multifrequency and multicomponent observations. Simulations performed here show that MEM is the best method of the four tested when attempting a reconstruction of the CMB signal. The final sky maps of the CMB produced with the Maximum Entropy algorithm, as well as maps of the various contaminants that the experiments are also sensitivity to, are presented. The maps from a range of different experiments can be used to put constraints on various cosmological parameters such as the density parameter, Ωo, Hubble's constant, Ho, and the spectral index of the large scale CMB power spectrum, n. Subsequent analysis performed on the sky maps is presented. These include examining the topology using genus as well as looking at the power spectrum and correlation functions. The methods discussed are first applied to simulations to test their usefulness at distinguishing between the origins of the fluctuations and then applied to the reconstructed CMB sky maps. New constraints on the power spectrum and some of the cosmological parameters will be given in the final chapter. Here, the data and analysis methods described will be summarised and the future of CMB experiments discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available