J. Muñoz: Cosmological puzzles from JWST

The launch of the James Webb Space Telescope (JWST) has ignited a revolution in our understanding of the early universe. Its exquisite infrared capabilities have allowed observers to find galaxies at higher redshifts and measure their stellar properties better than ever before. I will describe how, intriguingly, observations in different arenas appear to be in tension with our models. In short, there seem to be more galaxies, they are brighter, and emit more ionizing radiation. I will discuss how “universe breaker” galaxies are constrained by Hubble data, ruling out a cosmological departure from LCDM big enough to explain their abundances. Then, I will show how recent JWST determinations of reionization from galaxies are in tension with CMB and Lyman-alpha forest. Finally, if time allows, I will discuss the higher-than-expected abundance of early (z>9) galaxies in JWST and how to explain its origin.