2026-09-20T00:24:27Zhttps://dspace.mit.edu/server/oai/requestoai:dspace.mit.edu:1721.1/772552022-01-13T07:54:41Zcom_1721.1_7582com_1721.1_7581col_1721.1_131022
Jacqueline N. Hewitt.
Williams, Christopher Leigh
Massachusetts Institute of Technology. Dept. of Physics.
Massachusetts Institute of Technology. Department of Physics
2013-03-01T14:33:46Z
2013-03-01T14:33:46Z
2012
2012
http://hdl.handle.net/1721.1/77255
827335431
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).
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.
by Christopher Leigh Williams.
Ph.D.
194 p.
eng
Massachusetts Institute of Technology
M.I.T. theses are protected by
copyright. They may be viewed from this source for any purpose, but
reproduction or distribution in any format is prohibited without written
permission. See provided URL for inquiries about permission.
http://dspace.mit.edu/handle/1721.1/7582
Physics.
Initial exploration of 21-cm cosmology with imaging and power spectra from the Murchison Widefield Array
Thesis
application/pdf
false
Publication
unknown
unknown
<Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="b1aaff6a-af7a-436d-acf0-4e8386ad20c9">
<Type xmlns="https://www.openaire.eu/cerif-profile/vocab/COAR_Publication_Types">http://purl.org/coar/resource_type/c_1843</Type>
<Language>eng</Language>
<Title>Initial exploration of 21-cm cosmology with imaging and power spectra from the Murchison Widefield Array</Title>
<PublishedIn>
<Publication>
</Publication>
</PublishedIn>
<PublicationDate>2012</PublicationDate>
<Authors>
<Author>
<DisplayName>Williams, Christopher Leigh</DisplayName>
<Affiliation>
<OrgUnit>
</OrgUnit>
</Affiliation>
</Author>
</Authors>
<Editors>
</Editors>
<Publishers>
<Publisher>
<DisplayName>Massachusetts Institute of Technology</DisplayName>
<OrgUnit />
</Publisher>
</Publishers>
<License>http://dspace.mit.edu/handle/1721.1/7582</License>
<Keyword>Physics.</Keyword>
<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.</Abstract>
<Access xmlns="http://purl.org/coar/access_right"
>
</Access>
</Publication>