In the beginning: the first sources of light and the reionization of the universe

Contents 1. Preface: the frontier of small-scale structure 128 2. Hierarchical formation of cold dark matter halos 133 2.1. The expanding universe 133 2.2. Linear gravitational growth 135 2.3. Formation of non-linear objects 137 2.4. The abundance of dark matter halos 139 3. Gas infall and cooling in dark matter halos 144 3.1. Cosmological Jeans mass 144 3.2. Response of baryons to non-linear dark matter potentials 147 3.3. Molecular chemistry, photodissociation, and cooling 148 4. Fragmentation of the ÿrst gaseous objects 153 4.1. Star formation 153 4.2. Black hole formation 161 5. Galaxy properties 164 5.1. Formation and properties of galactic disks 164 5.2. Phenomenological prescription for star formation 165 6. Radiative feedback from the ÿrst sources of light The formation of the first stars and quasars marks the transformation of the universe from its smooth initial state to its clumpy current state. In popular cosmological models, the first sources of light began to form at redshift 30 and reionized most of the hydrogen in the universe by redshift 7. Current observations are at the threshold of probing the hydrogen reionization epoch. The study of high-redshift sources is likely to attract major attention in observational and theoretical cosmology over the next decade.