Dissertation Defense - Alex Reda - Yale University

Beam Calibration for the Canadian Hydrogen Intensity Mapping Experiment

 

Intensity mapping of the 21 cm line of neutral hydrogen is a promising new approach to charting the large scale structure of the Universe. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has played a crucial role in establishing the observational viability of this probe, recently achieving the first independent detection of the cosmological 21 cm power spectrum at redshift z ∼1. However, this detection is insensitive to the baryon acoustic oscillation (BAO) scale, a known standard ruler in cosmology whose evolution over cosmic time CHIME was built to measure to constrain the expansion history of the Universe and the underlying physics of dark energy. The large scales sensitive to BAO are obscured by bright astrophysical foregrounds which are 4-5 orders of magnitude brighter than the 21 cm signal; characterizing and removing these foregrounds requires exquisite control of the telescope beam response, which imprints spurious spectral structure on otherwise smooth foreground emission. I present a project which adapts the classic radio holography technique to address the challenge of beam calibration for a large telescope using stationary cylindrical reflectors. 

 

Thesis committee: Laura Newburgh (Advisor), Nikhil Padmanabhan, Karsten Heeger, Laura Havener, Laura Wolz (external reader)