It's Always Darkest Before the Cosmic Dawn: Results from First Generation 21 cm Interferometers and Lessons for the Next Generation
Realizing the promise of 21 cm cosmology to provide an exquisite probe of astrophysics and cosmology during the "Cosmic Dawn" and the epoch of reionization (EoR) has proven extremely challenging. We're looking for a small signal buried under foregrounds orders of magnitude brighter. We need large interferometers, precisely calibrated, producing mountains of data to to have any shot of seeing the signal. To confront this challenge, we need fast, robust, and rigorous statistical methods for turn that data in cosmologically interesting results. In this talk, I will survey the new statistical techniques we've developed and the progress we've made toward separating the 21 cm signal from foregrounds using current generation interferometers, the Precision Array for Probing the Epoch of Reionization (PAPER) and the Murchison Widefield Array (MWA). Then I will discuss how the progress we've made is now shaping the new Hydrogen Epoch of Reionization Array, a purpose-built interferometer designed not just to detect the EoR but to characterize its evolution, to push into the pre-reionization epoch, and to improve cosmological parameter constraints by eliminating the CMB's optical depth degeneracy.