The puzzling emergence of galaxies and black holes in the first billion years

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 event rates that early black holes could produce for the future LISA mission.