© Hanna Stacey
The most massive galaxies in the Universe stopped forming stars billions of years ago. How did these galaxies form and quench so rapidly? The canonical picture of galaxy evolution predicts that gas-rich mergers and active galactic nuclei (AGN) feedback are responsible, although these physical channels are largely unconstrained. Strong gravitational lensing can push the limits of observational astronomy to reach scales that are otherwise inaccessible, allowing us to advance our understanding of galaxy formation and AGN feedback. I will present recent investigations of gravitationally lensed dust and molecular gas in the host galaxies of quasars that test models of spheroid formation and AGN feedback at the peak of cosmic star formation.