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Jacqueline Hewitt. Ewall-Wice, Aaron Massachusetts Institute of Technology. Department of Physics. Massachusetts Institute of Technology. Department of Physics 2018-04-27T18:10:00Z 2018-04-27T18:10:00Z 2017 2017 http://hdl.handle.net/1721.1/115013 1029767890 Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2017. Cataloged from PDF version of thesis. Includes bibliographical references (pages 379-428). In this thesis, we take the first steps towards measuring the fluctuations in HI emission before reionization which carry information on the first X-ray emitting compact objects and hot interstellar gas heated by the deaths of the first stars (ancient demons). First, we show that existing and planned interferometers are sensitive enough to place interesting constraints on the astrophysics of X-ray heating. Second, we obtain first upper limits on the pre-reionization fluctuations with the Murchison Widefield Array. We also use these measurements to explore the impact of low-frequency systematics, such as increased foreground brightness and the ionosphere. We discover that contamination by fine-scale frequency structure introduced by the instrument is the leading obstacle to measuring the 21 cm power spectrum before reionization. This motivates the design of a next-generation experiment, HERA, with acceptable levels of intrinsic spectral structure. We also perform a careful examination of whether traditional calibration strategies are sufficient to suppress instrumental spectral structure. We find that while existing calibration techniques have critical flaws, there exist promising strategies to overcome these deficiencies which we are now pursuing. by Aaron Ewall-Wice. Ph.D. 428 pages eng Massachusetts Institute of Technology MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission. http://dspace.mit.edu/handle/1721.1/7582 Physics. Chasing ancient demons : tools for measuring 21 cm fluctuations before reionization Tools for measuring 21 cm fluctuations before reionization Thesis application/pdf false Publication unknown unknown <Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="fbe73ebd-58ae-43c8-b1d0-e25c754a4d45"> <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>Chasing ancient demons : tools for measuring 21 cm fluctuations before reionization</Title> <Subtitle>Tools for measuring 21 cm fluctuations before reionization</Subtitle> <PublishedIn> <Publication> </Publication> </PublishedIn> <PublicationDate>2017</PublicationDate> <Authors> <Author> <DisplayName>Ewall-Wice, Aaron</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>In this thesis, we take the first steps towards measuring the fluctuations in HI emission before reionization which carry information on the first X-ray emitting compact objects and hot interstellar gas heated by the deaths of the first stars (ancient demons). First, we show that existing and planned interferometers are sensitive enough to place interesting constraints on the astrophysics of X-ray heating. Second, we obtain first upper limits on the pre-reionization fluctuations with the Murchison Widefield Array. We also use these measurements to explore the impact of low-frequency systematics, such as increased foreground brightness and the ionosphere. We discover that contamination by fine-scale frequency structure introduced by the instrument is the leading obstacle to measuring the 21 cm power spectrum before reionization. This motivates the design of a next-generation experiment, HERA, with acceptable levels of intrinsic spectral structure. We also perform a careful examination of whether traditional calibration strategies are sufficient to suppress instrumental spectral structure. We find that while existing calibration techniques have critical flaws, there exist promising strategies to overcome these deficiencies which we are now pursuing.</Abstract> <Access xmlns="http://purl.org/coar/access_right" > </Access> </Publication>