Collaborative Research: Mapping the universe in neutral hydrogen with CHIME

Measurements of the spatial clustering of matter in the universe can reveal clues about the nature of the mysterious “dark energy” that is causing the universe’s expansion to accelerate. A new powerful way to measure this clustering at early epochs in the universe’s history is to use radio telescopes to detect the hydrogen gas that is ubiquitous in all galaxies. A team of scientists from Arizona State University, Massachusetts Institute of Technology, Yale University, and West Virginia University, is using a custom-built radio telescope, the Canadian Hydrogen Intensity Mapping Experiment (CHIME), to make one of the first measurements of dark energy from observations of radio waves emitted by hydrogen in the universe. This project will develop several new techniques to leverage the latest developments in signal processing, detector technology, and theoretical modeling. In parallel, this project will expand several outreach programs that teach high school and college-aged students about astronomy and scientific thinking. The goal of this project is to solve critical calibration and analysis challenges for CHIME that will reduce residual foreground contamination by an order of magnitude and enable the detection of the large-scale structure of the universe with the 21cm line, independent of other probes. CHIME’s recent measurements of cross-correlations between 21cm intensity maps and eBOSS galaxies up to redshift 1.4, and the Lyman-alpha forest up to redshift 2.3, have demonstrated CHIME’s potential for high-precision large-scale structure measurements. In this project, the team will develop new modeling frameworks and analysis pipelines for 21cm cross-correlations; generate improved beam models and integrate them into the analysis; implement new radio-frequency interference excision algorithms based on cyclostationary signal processing; and deploy innovative foreground filtering techniques that are robust to the dominant systematic errors in the data. These advances should lead to a CHIME-only auto-correlation detection of large-scale structure and ultimately the baryon acoustic oscillation signal. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.