Massive galaxies in the first billion years

Abstract

How did galaxies form and evolve in the early Universe? With the James Webb Space Telescope (JWST) and the Atacama Large Millimetre/submillimetre Array (ALMA), we can now study galaxies as they were within the first billion years after the Big Bang in unprecedented detail. In this thesis, we combine observations from these powerful telescopes to explore how some of the earliest massive galaxies formed stars, built up dust and heavy elements, and developed structure. We find galaxies that were already surprisingly evolved, with substantial amounts of dust and oxygen, and uncover a remarkably well-ordered rotating disc just 700 million years after the Big Bang. These discoveries raise fundamental questions about how rapidly galaxies could grow and evolve, offering new insights into the origins of galaxies like our own Milky Way.