Observing the Epoch of Reionization: Power Spectrum Limits and Commissioning Next Generation 21 cm Experiments

As one of the last unobserved frontiers in the Universe, the Epoch ofReionization (EoR) marks the period when the Universe transitioned from a neutral state to anionized state, marking the last global phase change. Understanding how the EoRevolved over time and when it occurred will provide evidence for the nature ofthe first luminous sources of the Universe. Specifically, we'll be able toanswer questions such as what were the first galaxies like in terms of theirluminosities, masses, and spectral energy distributions? Were they similar totodays galaxies? How did they form? How were they spatially distributed? Thesequestions and many others begin to probe the early times of galaxy formation, afield in need of observations of the earliest galaxies.In the first chapter, I provide an introduction to 21 cm cosmology, which usesthe 21 cm line transition from neutral hydrogen to study the evolution of theUniverse. I briefly review 21 cm physics and the evolution of thecosmological 21 cm signal. The challenges of experiments measuring highlyredshifted neutral hydrogen are discussed before describing the instrumentsused to make the measurements of the cosmological 21 cm signal.The second chapter in this thesis begins by presenting results from Donald C.Backer Precision Array for Probing the Epoch of Reionization (PAPER) 64 antennaconfiguration. I start by describing the dataset used in the chapter, followed by the novelredundant calibration technique used to calibrate the grid layout of the PAPER array.I then discuss the application of delay and fringe-rate filtering to suppress foregrounds andoptimally combine time samples, respectively. Before presenting results, Ilayout a quadratic estimator formalism for measuring the 21 cm power spectrum.I finally present the results from the PAPER-64 dataset.The third chapter of this thesis shifts focus to the new Hydrogen Epoch ofReionization Array (HERA), a close packed, redundant, low frequency arraydedicated to detecting and characterizing the EoR and Dark Ages. As a newexperiment with terabytes of data being collected per day, the need for a realtime processing system is necessary to avoid a backlog of data and to avoiddata storage issues. I present the real time system (RTS) developed foranalyzing HERA data, which automatically detects and flags bad antennas,redundantly calibrates the array, and excises radio frequency interference(RFI) in real time. This work builds off the lessons learned from PAPER andthe Murchison Wide-Field Array (MWA) based in western Australia. I then presentsome initial results from the RTS system.In the final chapter, I conclude the thesis by summarizing the work presented and discussfuture directions for 21 cm cosmology