I am a radio astronomer who focuses on observational cosmology measurements. 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.
Radio Cosmology
Image source: NASA / LAMBDA Archive / WMAP Science Team
Understanding the universe’s evolution requires precise measurements of distant objects with light travel times of millions or billions of years. We can use radio telescopes to map low-frequency emission lines, and my work focuses on the 21 cm emission line from neutral hydrogen.
Measuring 21 cm emission across cosmic time, or redshift, has the potential to map out the universe’s history in great detail. These measurements would reveal the universe’s large-scale structure during the cosmic Dark Ages, the Cosmic Dawn (when the first stars and galaxies appeared), the Epoch of Reionization (EoR, when early stars and galaxies ionized the intergalactic medium), and throughout the universe’s subsequent cosmological expansion.
My research focuses on answering 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? What is the universe’s expansion history?
Precision Analysis Techniques for Radio Astronomy
Radio cosmology measurements require exquisite precision to extract faint cosmological signals from noisy data. My research program specializes in novel data analysis techniques that can achieve the precision needed for cosmology measurement and other precision radio astronomy applications.
One facet of my research focuses on calibration. 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 we developed new approaches for characterizing calibration error and developed new calibration strategies based on maximum likelihood and Bayesian statistical techniques.
We have also developed new techniques for reconstructing polarized radio emission with high precision. Polarized signals reveal the structure of magnetic fields in the interstellar medium, trace auroral emission of exoplanets, and are a significant contaminate of 21 cm cosmology measurements.
My research leverages high performance computing techniques that allow our analyses to keep pace with the massive data volumes generated by modern radio telescopes. For example, we developed a cloud-based analysis pipeline using Amazon Web Services (AWS).
In a figure from our paper on Delay-Weighted Calibration, or DWCal, we show that our technique delivers about 2 orders of magnitude better calibration precision than standard radio astronomy techniques.
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.
Characterizing the Diffuse Radio Sky
In the last half century, radio astronomers have measured and catalogued hundreds of thousands of compact radio sources. However, our understanding of diffuse radio structures that span several degrees or more is limited.
To remedy this, 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 helps us to calibrate our telescopes for 21 cm cosmology measurements.
Forthcoming work from my group will map low-frequency diffuse emission with the OVRO-LWA telescope, generating the highest fidelity maps of this kind to date.
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.
Designing Next-Generation Radio Telescopes
Artist’s rendering of the forthcoming DSA-2000 telescope.
As radio astronomy instrument improves and computational hardware becomes more capable, astronomers have the opportunity to make ever more sensitive measurements. My research is interested in guiding the design of these next-generation telescopes to maximize their science output.
I am a member of the DSA-2000 project, a forthcoming telescope to be built in Nevada. In a recent paper, we projected the sensitivity of the DSA-2000 to the cosmological 21 cm signal, and made recommendations for the configuration of the array.