Research Focus: 21 cm Cosmology

My research focuses on 21 cm cosmology. Our goal is to map the early universe, from the first stars through to the Epoch of Reionization, during the period known as the “Cosmic Dawn,” roughly the first billion years after the Big Bang. We use the 21 cm transition of neutral hydrogen to trace the temperature, density, and ionization state of the intergalactic medium — the gas between galaxies — to learn about the first luminous objects in the universe via their effect on the surrounding gas. Detecting and characterizing that signal will allow us to directly study the astrophysics of reionization and eventually to make precise measurements of cosmological parameters.

 By surveying the early universe topographically with redshifted 21 cm radiation, we hope to make precise measurements of the conditions and evolution of the universe during the “Cosmic Dawn” that took place during the first billon years.  Image Credit: Scientific American.

By surveying the early universe topographically with redshifted 21 cm radiation, we hope to make precise measurements of the conditions and evolution of the universe during the “Cosmic Dawn” that took place during the first billon years. Image Credit: Scientific American.

Though a vast amount of information is potentially accessible by tomographically mapping the early universe with low frequency radio waves, that signal is dwarfed by enormous foregrounds and significant noise. This means that we need large, specially designed radio interferometers like the Hydrogen Epoch of Reionization Array (HERA) to measure these faint signals.

 A rendering of the 320 dishes in the core of HERA, currently under construction in the Karoo Desert in South Africa.  Image Credit: Dave DeBoer

A rendering of the 320 dishes in the core of HERA, currently under construction in the Karoo Desert in South Africa. Image Credit: Dave DeBoer

My work has focused on developing and applying robust data analysis techniques for separating those foregrounds from the cosmological signal and then maintaining that separation despite real-world challenges. I am actively interested in all stages of that analysis, from raw bits from the correlator to constraints on astrophysical and cosmological parameters.


More generally, I'm interested in:

  • Next generation radio interferometers that precisely map neutral hydrogen in the universe at increasing sensitivities and resolutions.

  • Calibration, mapmaking, power spectrum estimation, and other forms data analysis and data reduction for large interferometric arrays.

  • Analysis tools that preserve cosmological information and make it possible to take advantage of large data sets.

  • Forecasting future arrays and optimizing them for making various cosmological measurements.

  • Connecting 21 cm cosmology with other probes to learn more about the Epoch of Reionization and the Cosmic Dawn.