The Past, Present, and Future of 21cm Cosmology
Despite tremendous recent progress, gaps remain
in our knowledge of our cosmic history. For example, we have yet to make
direct observations of Cosmic Dawn or the subsequent Epoch of
Reionization. Together, these represent the important period when the first
stars and galaxies were formed, dramatically altering their surroundings
in the process. Radio telescopes targeting the 21cm line will open up
these crucial epochs to direct observations in the next few years, filling
in a missing chapter in our cosmic story. I will review our recent results
from the Precision Array to Probe the Epoch of Reionization (PAPER)
experiment. These results have begun to shed light on heating
processes during reionization. I will also motivate unconventional ideas
in experiment design that have been proposed and implemented to deal with
the unique technical challenges of 21cm cosmology. Cognizant of
"lessons learned" from the current generation of instruments, I will
describe our recently commenced Hydrogen Epoch of Reionization Array
(HERA), including its forecasted promise to provide exquisite constraints
on reionization astrophysics as well as on fundamental parameters such as
the neutrino mass.