Katherine Whitaker

When the universe was merely three billion years old, about half of massive galaxies had already formed the bulk of their stars and new star formation plummeted. How these 'red and dead' (quiescent) galaxies quench at such early times remains a puzzle, as their dark matter halos contain large gas reservoirs. This gas should cool efficiently, sustaining star formation over long periods.  In this talk, I will review the recent innovative techniques developed to probe the physical properties of early quiescent galaxies, and the key observations constraining their formation histories.   I will present promising paths forward towards solving this puzzle that leverage strong gravitational lensing and the capabilities of the Hubble Space Telescope and ALMA, as well as a look toward the future with exciting upcoming public facilities.