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Paper: The First Billion Years: Probing Reionization as well as the Inflationary Initial Conditions
Volume: 395, Frontiers of Astrophysics: A Celebration of NRAO's 50th Anniversary
Page: 59
Authors: Loeb, A.
Abstract: The cosmic microwave background provides an image of the universe 0.4 million years after the big bang, when atomic hydrogen formed out of free electrons and protons. One of the primary goals of observational cosmology is to obtain follow-up images of the universe during the epoch of reionization, hundreds of millions of years later, when cosmic hydrogen was ionized once again by the UV photons emitted from the first galaxies. To achieve this goal, new observatories are being constructed, including low-frequency radio arrays capable of mapping cosmic hydrogen through its redshifted 21 cm emission as well as imagers of the first galaxies such as the James Webb Space Telescope (JWST) and large-aperture ground-based telescopes. The construction of these observatories is being motivated by a rapidly growing body of theoretical work illustrating how the fluctuations in the 21 cm brightness from cosmic hydrogen were sourced by the primordial density perturbations from inflation as well as by the radiation from galaxies. Numerical simulations of reionization are starting to achieve the dynamical range required to resolve galactic sources across the scale of hundreds of comoving Mpc, larger than the biggest ionized regions.
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