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

  • Author(s): Ali, Zaki Shiraz
  • Advisor(s): Parsons, Aaron R
  • et al.

As one of the last unobserved frontiers in the Universe, the Epoch of

Reionization (EoR) marks the period when the Universe transitioned from a neutral state to an

ionized state, marking the last global phase change. Understanding how the EoR

evolved over time and when it occurred will provide evidence for the nature of

the first luminous sources of the Universe. Specifically, we'll be able to

answer questions such as what were the first galaxies like in terms of their

luminosities, masses, and spectral energy distributions? Were they similar to

todays galaxies? How did they form? How were they spatially distributed? These

questions and many others begin to probe the early times of galaxy formation, a

field in need of observations of the earliest galaxies.

In the first chapter, I provide an introduction to 21 cm cosmology, which uses

the 21 cm line transition from neutral hydrogen to study the evolution of the

Universe. I briefly review 21 cm physics and the evolution of the

cosmological 21 cm signal. The challenges of experiments measuring highly

redshifted neutral hydrogen are discussed before describing the instruments

used 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 antenna

configuration. I start by describing the dataset used in the chapter, followed by the novel

redundant 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 and

optimally combine time samples, respectively. Before presenting results, I

layout 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 of

Reionization Array (HERA), a close packed, redundant, low frequency array

dedicated to detecting and characterizing the EoR and Dark Ages. As a new

experiment with terabytes of data being collected per day, the need for a real

time processing system is necessary to avoid a backlog of data and to avoid

data storage issues. I present the real time system (RTS) developed for

analyzing 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 and

the Murchison Wide-Field Array (MWA) based in western Australia. I then present

some initial results from the RTS system.

In the final chapter, I conclude the thesis by summarizing the work presented and discuss

future directions for 21 cm cosmology.

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