Line Intensity Mapping the Epoch of Reionization with the Fred Young Submillimeter Telescope

Abstract

The baryonic matter in the universe is primarily hydrogen and helium gas, which existed in a neutral atomic state for approximately 400 thousand years following the Big Bang. With the formation of the first galaxies, their ionizing far-UV radiation initiated the ionization of intergalactic hydrogen, and later of helium. The ionization of hydrogen occurred between approximately 300 to 1000 million years after the Big Bang (redshift 11 to 6), a period referred to as the Epoch of Reionization (EoR). The majority of the early galaxies responsible for the reionization are too faint to be detected individually by current observational methods. However, line intensity mapping (LIM) is a novel technique that complements traditional galaxy surveys by capturing the aggregated emission from galaxies within a particular volume in both angular and frequency space, including those too faint to be detected individually. <br/> This thesis develops models for forecasts of observations with a forthcoming LIM survey at 205 to 440 GHz using the Fred Young Submillimeter Telescope (FYST). Specifically, we predict the power spectrum (PS) of the singly ionized carbon, [CII] 158 μm (1900.5 GHz), fine-structure line emission from EoR galaxies. Our model is based on the IllustrisTNG300 hydrodynamic simulation. We find that a detection of the galaxy PS would be possible at redshift bins z=3.4-3.9, 4.1-4.8, 5.3-6.3, and a detection may be possible at z=6.8-8.3. <br/> However, our predictions did not account for the detrimental, contaminating effect of carbon monoxide (CO) rotational line emission from lower-redshift (foreground) galaxies. These lines overlap in frequency with the higher redshift [CII] emission, and their signal must be separated or suppressed in order to detect the [CII] PS. <br/> The second part of this thesis also models the CO emission and evaluates the effectiveness of a foreground masking technique. Our findings indicate that [CII] emission dominates over CO emission above 300 GHz. However, extensive masking is necessary at lower frequencies to detect [CII]. We anticipate the recovery of the [CII] PS at z=3.4-3.9 and z=4.1-4.8, and likely also at z=5.3-6.3. However, at z=6.8-8.3 this is most challenging, necessitating the development of more effective strategies.