Affiliation: University of Geneva

Contribution: Invited

Title: Focus on: Galaxy Formation – the first Gyr (Observations)

Abstract: The first deep images with the James Webb Space Telescope (JWST) have transformed our view of the Universe. From day one, JWST produced one surprise after another: from unexpectedly luminous candidate galaxies at z>10, to an abundant, new class of obscured black holes, to massive quiescent galaxies when the Universe was only 1-2 Gyr old. With its unparalleled imaging and spectroscopic capabilities, JWST immediately extended our cosmic horizon into uncharted territory, with galaxies spectroscopically confirmed to z~14 and candidates identified out to z~16, only ~250-300 Myr after the Big Bang. We are thus at the brink of finding the first galaxies that ended the cosmic Dark Ages and started the reionization of the Universe. Furthermore, JWST finally provides resolved, deep rest-frame optical observations to z~10 – a huge leap from the previous limit at z~3 with HST. This finally allows us to select mass-complete samples of galaxies in the first 1 Gyr of cosmic history, measure their redshifts, and characterise their physical properties. In this talk, I will show how far we have come in understanding early galaxy build-up over the last years. I will start with the state of knowledge from three decades of Hubble and Spitzer Space Telescope datasets, and will review our current understanding of early galaxies based on the first ~2 years of revolutionary JWST data.

This contribution can be found here (pdf).