Initial exploration of 21-cm cosmology with imaging and power spectra from the Murchison Widefield Array
Name
827335431-MIT.pdf
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Full printable version
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6.31 MB
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fa2c90bb9a2fd68007356f544b11738b
Author(s)
Williams, Christopher Leigh
Advisor(s)
Jacqueline N. Hewitt.
Date Issued
2012
Publisher
Massachusetts Institute of Technology
Abstract
The Murchison Widefield Array (MWA) is a new low-frequency radio array under construction in Western Australia with a primary goal of measuring the power spectrum of the 21-cm signal from neutral hydrogen during the Epoch of Reionization (EoR). In this thesis, we detail efforts to characterize the MWA system, and present scientific results from a 32-element prototype interferometer deployed at the MWA site. We develop simulations and perform anechoic chamber measurements to verify the performance of the MWA antenna tiles. We develop a calibration and imaging pipeline for the MWA which uses w-projection widefield imaging techniques and direction-dependent point spread functions. Using data from an MWA expedition in March 2010, we produce confusion-limited maps covering ~ 2700 square degrees in a region of sky with low galactic temperature. We develop a blind source detection and extraction algorithm, and use it to perform a blind survey in these maps, and detect 655 sources at high significance with an additional 871 candidates. We compare these sources with existing low-frequency radio surveys in order to assess the MWA-32T system performance, and to identify new candidates for ultra-steep spectrum radio sources. In order to constrain the EoR, we apply two power spectrum estimation techniques to this dataset: a Fast Fourier Transform in order to rapidly compute power spectra, and a quadratic estimation method which uses inverse covariance weighting to produce an optimal estimate. We use a principal component analysis to identify and remove the foreground contaminants. In the resulting two-dimensional power spectra, we find the predicted "wedge" feature due to the chromaticity of the instrumental response, and identify a sensitive region free of strong contaminants which can be used for characterizing the EoR signal. We then use these data to produce new limits on the EoR power spectrum at z = 9.
Description
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 189-194).
Subjects
Physics.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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