It's Always Darkest Before the Cosmic Dawn: Early Results from Novel
  Tools and Telescopes for 21 cm Cosmology
  21 cm cosmology, the statistical observation of the high redshift universe
using the hyperfine transition of neutral hydrogen, has the potential to
revolutionize our understanding of cosmology and the astrophysical processes
that underlie the formation of the first stars, galaxies, and black holes
during the "Cosmic Dawn." By making tomographic maps with low frequency radio
interferometers, we can study the evolution of the 21 cm signal with time and
spatial scale and use it to understand the density, temperature, and ionization
evolution of the intergalactic medium over this dramatic period in the history
of the universe.
  For my Ph.D. thesis, I explore a number of advancements toward detecting and
characterizing the 21 cm signal from the Cosmic Dawn, especially during its
final stage, the epoch of reionization. In seven different previously published
papers, I explore new techniques for the statistical analysis of
interferometric measurements, apply them to data from current generation
telescopes like the Murchison Widefield Array, and look forward to what we
might measure with the next generation of 21 cm observatories. I focus in
particular on estimating the power spectrum of 21 cm brightness temperature
fluctuations in the presence enormous astrophysical foregrounds and how those
measurements may constrain the physics of the Cosmic Dawn.
  Thesis Supervisor: Max Tegmark
