UC Berkeley

The path towards detecting the cosmological 21 cm signal from the Epoch of Reionization and Cosmic Dawn has seen tremendous progress over the past decade: interferometric experiments have placed increasingly stringent upper-limits on the 21 cm power spectrum, and global signal experiments have made a tentative first-detection of the 21 cm monopole signal. As next-generation experiments are designed, built, and begin taking data, the road towards maximizing their scientific potential hinges crucially upon the development of robust data analysis techniques for isolating the 21 cm signal from foregrounds and low-level instrumental systematics. This thesis is a compilation of work that describes new and old techniques and applies them to the up-and-coming Hydrogen Epoch of Reionization Array (HERA), a second-generation low-frequency experiment that aims to make a detection of the 21 cm power spectrum from redshifts 6 < z < 20. Such a feat would dramatically improve our understanding of the intergalactic medium at these redshifts, and would shed light on the formation and properties of the first stars, galaxies, and compact objects in the universe. Towards this goal, this work touches on some of the current challenges facing the analysis of 21 cm data, from instrument commissioning and calibration to astrophysical parameter inference. In particular, we develop a detailed understanding of low-level systematics in the HERA system, yielding improved sensitivity in the measured power spectrum by over two orders of magnitude. As HERA construction is finished and full-sensitivity observing commences, the algorithms and analysis frameworks discussed here are setting the stage for a future full-sensitivity HERA analysis and the next-generation of 21 cm cosmology.