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UBC Theses and Dissertations

Towards precision measurements of the Hubble constant with the Canadian Hydrogen Intensity Mapping Experiment Pinsonneault-Marotte, Tristan


The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a transit interferometer located at the Dominion Radio Astrophysical Observatory in Penticton, BC. It is designed to map large- scale structure in the universe by observing 21 cm emission from the hyperfine transition of neutral hydrogen between redshifts 0.8 and 2.5. CHIME will perform the largest volume survey of the universe yet attempted and will characterize the BAO scale and expansion history of the universe with unprecedented precision in this redshift range. CHIME achieved first light in the fall of 2017 and instrument commissioning is underway. In this work I present sensitivity forecasts and derive constraints on cosmological parameters given CHIME’s nominal survey. The broad redshift range of the observations will enable tight constraints to be placed on the Hubble constant H0 , independent of CMB or local recession velocity measurements. Precision measurements of this epoch will shed new light on the tension between direct measurements of the Hubble constant vs. those inferred from high-redshift observations, notably the CMB anisotropy. CHIME measurements together with a prior on the baryon density from measurements of deuterium abundance are enough to place constraints on H0 at the 0.5% level assuming a flat ΛCDM model, with uncertainty increasing to ∼ 1% if curvature is allowed to vary, or up to ∼ 3% for a dark energy equation of state with w/= −1. Including priors from CMB measurements, in the scenario where the datasets are consistent, narrows these uncertainties further, most significantly in the model where w is a free parameter.

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