Princeton University Thunch Talk

One of the unsolved problems in extragalactic astronomy is understanding the physics of how the most distant massive galaxies grow their stellar mass over cosmic time. Large-scale hydrodynamical simulations have been largely successful in matching the basic properties and number densities of these galaxies at z < 2.5 (covering the past 11 Gyr). This has given us confidence in our understanding of the physics that regulates star formation and quenching over most of cosmic history. However, at earlier times, simulations underestimate the number densities of massive quiescent galaxies by a shocking 1-2 orders of magnitude. Recent JWST discoveries of massive galaxies observed at even earlier times than we thought possible have brought this tension with theory back to the limelight. In this talk, I will give an overview of the systematics contributing to this discrepancy between theory and observations, as well as our best attempts at addressing it using (1) medium-band galaxy surveys; (2) novel color-color selection methods; (3) physically motivated star-formation histories; and (4) detailed spectroscopic characterization.