My research uses radio telescopes to better understand the structure and evolution of our universe. I work to answer questions like, When did stars and galaxies appear? How big were the first galaxies? What physics governed their formation? What role did Dark Matter play in the universe’s evolution?
In particular, I am interested in a field of observational cosmology called “21 cm cosmology” that leverages emission from neutral hydrogen to study the early universe. 21 cm cosmology has the potential to revolutionize our understanding of cosmological history, but only if we can build and operate sufficiently sensitive radio telescopes. I specialize in developing new precision radio astronomy techniques that allow us to measure signals—including the 21 cm signal—that would otherwise be too distant and faint to detect.
For a full list of my publications, see my ORCID profile. More information about the telescopes I use is available here, and my CV is available here.
Precision Calibration
Calibration is a major challenge for 21 cm analyses. The calibration process determines the sensitivity of each antenna in the array by matching the data to an expected signal. Traditional radio interferometric calibration doesn’t deliver the precision we need to measure faint cosmological signals, so more advanced methods are required. A major component of my research is characterizing calibration error and developing new calibration strategies.
Unified calibration is a new calibration technique we developed that combines aspects of two established calibration approaches, sky-based calibration and redundant calibration. We show that unified calibration performs better than either those approaches when calibrating noisy data in the presence of sky model error.
Delay-weighted calibration, or DWCal, is another novel calibration technique we designed to improve calibration performance when calibrating to an imperfect sky model. Here we show that DWCal improves our measurement sensitivity by two orders-of-magnitude when compared with a standard sky-based calibration approach.
Understanding the Diffuse Radio Sky
We created a map of diffuse, polarized radio emission across a huge swath of the Southern Hemisphere sky using data from the MWA telescope. This map reveals the structure of the Milky Way’s interstellar medium, provides clues about Galactic magnetic fields, and (most importantly for us observational cosmologists) it helps us to calibrate our telescopes for 21 cm cosmology measurements.
Here we show a map of unpolarized radio emission at scales of 1-9 degrees. For more information about this map and to see its polarized counterparts, check out Byrne et al. 2022.
Polarimetry
I developed a data analysis pipeline that produces fully-polarized analyses. Along the way I learned a lot about polarized sky signals, polarized telescope measurements, and what they can tell us about one another. Understanding polarized radio emission helps mitigate signal contamination for 21 cm cosmology measurements. We can also use these techniques to detect auroral emission from exoplanets.
A telescope’s response to polarized emission can be complicated, especially for widefield instruments that see the whole sky. Here we plot the expected polarized response of an antenna from the MWA telescope. See our paper for more information about working with these polarized responses.
Cloud Computing
Radio telescopes produce massive data volumes, and the analyses required to extract signals from that data can be very computationally intensive. It is a constant challenge to find efficient, scalable analyses approaches. I developed a cloud-based analysis pipeline using Amazon Web Services (AWS).
Our cloud-based analysis pipeline automatically starts and stops instances for data processing. This lets us have all the compute power we need and charges us only for what we use.