ABSTRACT

The launch of the James Webb Space Telescope (JWST) has ignited a revolution in our understanding of the early universe. JWST observations are revealing a bursty active universe, with far more bright galaxies than expected, and I will show the ways these data intriguingly depart from our models. I will first discuss the higher-than-expected abundance of early (redshift z>9) galaxies in JWST, and show how clustering measurements are key for understanding how these galaxies formed. Then, I will discuss how recent JWST determinations of the ionizing properties of the first galaxies are in tension with CMB and Lyman-alpha forest observations. Finally, I will briefly touch on the ultra-massive galaxy candidates recently argued to "break" our cosmological model (LCDM), and how HST disfavors a cosmological explanation of their abundances.

About the Speaker:

Julian Munoz is an Assistant Professor in the Department Astronomy at the University of Texas at Austin since 2023. He finished his Bachelor's degree at the Complutense University of Madrid in 2013, and his PhD in Physics at Johns Hopkins University in 2017. After that, Julian was a postdoctoral fellow at the Harvard Physics Department until 2020, and a Clay Fellow at the Harvard-Smithsonian Center for Astrophysics until 2022. Julian works on understanding the elusive dark matter and its connection to the formation of the first galaxies. He uses techniques ranging from pen-and-paper calculations to computer simulations to confront his theories to cosmological observations. He is best known for his work on detecting dark matter with the 21-cm signal, and for developing a new standard ruler at high redshifts. He has recently been selected one of Science News 10 scientists to watch in 2023.