The Murchison Widefield Array (MWA) Epoch of Reionization Project.  The MWA is a low-frequency radio telescope facility in Western Australia.  Detecting the 21 cm signal from hydrogen gas during the Epoch of Reionization (EoR) is one of its principal science goals, and our group has played a significant role in advancing this research.  After the telescope underwent a Phase II upgrade in 2016, we were the first group to study the new redundant calibration approach enabled by the upgrade, and we have since published some of the most stringent limits on the 21 cm signal to-date using MWA Phase II data.  Phase III of the experiment began at the start of 2022 and represents another major upgrade in capability for the telescope.

Lunar Array Design.  21 cm emission from some of the highest redshifts cannot be observed from the ground due to the Earth’s ionosphere.  Plans to build space- or lunar-based radio arrays capable of observing this emission have been in development for many years, but these observations are far more challenging than those already being conducted from the ground and will require meticulous design.  Our group uses our expertise in interferometric simulation to test design concepts and study how antenna and array designs might be optimized for this ambitious science case.

Machine Learning for 21 cm Cosmology.  Machine Learning (ML) refers to a wide variety of techniques, many of which have the potential to address difficult problems in 21 cm cosmology.  My group has explored several applications of ML, including the development of convolution neural networks for the identification of contaminating human-generated radio signals in data from HERA and the recovery of cosmological parameters from simulations of the 21 cm signal. Current research is largely done in collaboration with Prof. Stephen Bach in Brown’s Computer Science Department.

The Radio Astronomy Software Group.  Recognizing the need for reliable and robust software pipelines, my colleagues and I created the Radio Astronomy Software Group (RASG) in 2015 to provide open-source tools which can interface with our data and telescope models at a foundational level.  Our group at Brown is a significant contributor to all RASG projects and leads the development of pyuvsim, a code which provides extremely high precision simulations of mock radio interferometric data.

The Hydrogen Epoch of Reionization Array (HERA).  Located in the Karoo desert of South Africa, HERA is an experiment with the express purpose of detecting the 21 cm hydrogen signal from the EoR.  HERA construction is nearly complete and the first limits on the 21 cm signal from early data have been published.  Our group has contributed to HERA design, commissioning, and analysis over the years.

Bayesian Power Spectrum Analysis.  Analysis for 21 cm cosmology requires extremely precise models of the radio telescopes doing the observation to distinguish foreground emission from the hydrogen signal.  A Bayesian framework provides a natural way to account for uncertainties in the sky and instrument models and disentangle the contributions of different components to the overall observed data — but, computationally, such a treatment is very demanding.  Our group has led the development of BayesEoR, a new power spectrum analysis code that balances these trade-offs.

The Precision Array for Probing the Epoch of Reionization (PAPER)PAPER was a first-generation 21 cm cosmology experiment in the Karoo desert of South Africa that operated from 2009 – 2016.  Prof. Pober was one of the lead data analysts for the early stages of the experiment.  At Brown, our group contributed to the re-analyses of PAPER data that ultimately established the final limits made by the experiment.  PAPER has since been decommissioned and replaced by HERA.