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Finding constraints on dark energy using hydrogen intensity mapping Fink, Allison

Abstract

In this MS.c. thesis, we demonstrate a method for estimating the expansion history of the universe using the hydrogen intensity map from the Canadian Hydrogen Intensity Mapping Experiment (CHIME), which will be generated in the near future. This map will be in angular and redshift space, where redshift of the hydrogen due to the expansion serves as a time variable. The expansion history, dependent on cosmological parameters via the Einstein equations, determines the distance away from us in units of a grid comoving with the expansion at which light of each redshift was emitted. We use knowledge of the fixed comoving distance, approximately 150 megaparsecs, that baryon acoustic oscillations, or primordial sound waves, traveled away from the centers of matter perturbations, where there is a corresponding peak in the matter correlation function subject to uncertainty of the initial quantum mechanical fluctuations. We explain the method by which we fit the correlation function to a model for expansion determined by the equation of state of dark energy, to constrain this parameter. We test the method using a three-dimensional realization of the theoretical matter power spectrum calculated from CAMB (Code for Anisotropies in the Microwave Background), providing an estimate of constraints obtained from a small redshift region spanning one sound horizon diameter in redshift space assuming a constant equation of state of dark energy and fixed values of the other cosmological parameters. We explain how to generalize this method to a more complete analysis.

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Attribution-NonCommercial-NoDerivatives 4.0 International

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