ASU professor part of award-winning team for research on mapping the universe

Simon Foreman, an assistant professor for the Department of Physics at Arizona State University, was part of a team to win this year’s first-place Buchalter Cosmology Prize. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) Collaboration was recognized for its measurements of the clustering of hydrogen gas over a large region of the observable universe.

Their paper was commended by the judging panel for providing a promising approach to mapping the large-scale structure of the universe and taking a step closer to understanding the nature of dark energy.

The research focused on 21 cm intensity mapping, a way to probe the cosmic distribution of matter using measurements of radiation emitted by neutral hydrogen clouds. This is the first such measurement made with an instrument customized for intensity mapping, and the highest-redshiftThe light from an object moving away from the observer. 21 cm intensity mapping measurement ever made at the time of the publication, which has now been surpassed by a later CHIME analysis.

The wavelength of the emitted radiation is stretched by the universe's expansion, with the stretching depending upon the distance between the source and its observer. Measuring this radiation at wavelengths greater than 21 cm tells researchers about galaxies that are farther away, allowing for the construction of a 3-dimensional map of their distribution.

Foreman co-developed the simulation and theory-interpretation pipelines to complete the analysis.

“By mapping the distribution of atomic hydrogen through cosmic history and over large volumes of the universe, there is a huge amount we can learn: the details of the accelerating expansion of the universe, the role of hydrogen in galaxy formation and evolution and the physical processes at play in the very early universe,” said Foreman.

“However, this field is still in its infancy: only a few measurements using this 21 cm intensity mapping technique have been made so far. CHIME’s measurement is an important step forward, demonstrating that a custom-built instrument can measure the 21 cm signal and paving the way for more precise measurements that use the full power of CHIME’s dataset.”

CHIME itself is a radio telescope built to observe at these wavelengths. Based in British Columbia, Canada, its data was used to measure the statistical correlation between the brightness of its sky maps and the positions of galaxies measured by the Sloan Digital Sky Survey.

Foreman has been involved with CHIME since before coming to ASU in 2023; he is currently building a research group that will advance the telescope’s scientific goals. CHIME had its first meeting in the United States in December with support from the Beus Center for Cosmic Foundations to make progress towards future analyses of CHIME data.

“It’s exciting to be at the cutting edge, developing new methods and making measurements that have never been made before. We still have a ways to go before we can obtain precise cosmological information from CHIME, but this project demonstrates that we’re making steady progress, and we expect more exciting results in the coming years,” said Foreman.