Topic: reionization

JWST observations reveal sources earlier and brighter than anticipated. This talk examines their implications for cosmological and galaxy-formation models. It considers the unexpectedly numerous galaxies during the first few hundred million years, at redshifts above nine, and how cosmological clustering measurements can distinguish competing explanations. It then presents an initial empirical measurement of the dependence of star-formation variability, or burstiness, on galaxy mass, which may help explain the excess. Finally, it discusses tensions between JWST measurements of reionization and

Fraser Cain and Pamela L. Gay explore what cosmology can establish about the universe’s earliest history and where knowledge remains limited. The discussion covers inflation, the separation of forces, the emergence of particles and nuclei, and density fluctuations that seed later structure. Recombination and the cosmic microwave background lead into the dark ages, the first stars and reionization, with observations including JWST helping test models of the early universe. Pamela Gay is a senior scientist at the Planetary Science Institute. This Astronomy Cast episode was published on 14 Septem

Pratika Dayal examines galaxy and black-hole formation during the first billion years, when the first galaxies ended the cosmic dark ages and began reionizing intergalactic hydrogen. JWST has revealed unexpectedly abundant, massive black holes, reaching about one hundred million solar masses within the first six hundred million years, challenging formation models. These observations can constrain the progress and spatial structure of reionization in preparation for 21-centimeter measurements. Early galaxies also test alternatives to cold dark matter. The talk considers the gravitational-wave e