This thesis describes the characterisation of non-Gaussianity in the Cosmic Microwave Background (CMB) from observations made with the Very Small Array (VSA) and the Cosmic Background ~mager (CBI). The VSA and the CBI are interferometric instruments designed to image the CMB at angular scales correspondIng to mUltipoles up to .e = 3500. An overview of radio interferometry is given. The experimental challenges related to the obse~vation of the CMB are discussed, and how interferometry is particularly well suited to deal with them. The VSA and the CBI are described. The data reduction processes in both instruments are outlined, as well as the measures adopted to control systematic effects and remove contamination of instrumental and astrophysical origin. The characterisation of non-Gaussianity for this thesis was based on the bispectrum, for which a weighted variance estimator and two normalised estimators were implemented. Null hypothesis tests show that, overall, the VSA data set and the CBI field deep20hr are consistent with Gaussianity. A theoretical bispectrum was used, together with the normalised bispectra estimates from the data to place limits on the non-linear coupling parameter fNL. We combined fNL limits from 32 VSA fields to find a combined limit of IfNLI < 2732. A subset of the VSA data was used to explore the possibility of detecting a bispectrum signal from bright point sources. There is not evidence to suggest that the estimators used in this thesis can be used to detect such signal in the VSA data in a consistent maner. Additions and improvements to the non-Gaussianity tests applied in this work are discussed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:505386 |
| Date | January 2009 |
| Creators | Blanco, Francisco |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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