Astronomy Colloquium

Today's galaxy population shows a large structural diversity that depends on stellar mass, star-formation activity, and environment. Even quiescent galaxies that have little star formation display a large range of morphological properties, indicating several different formation mechanisms at work. The peak of cosmic star formation rate density at redshifts of 1 to 3 is thought to be the epoch of the major buildup of these massive spheroids. By combining ground-based SINFONI integral-field unit observations with Hubble Space Telescope imaging data, I will show how these early galaxies grow on spatially resolved scales, and how they transition to the quiescent population. In particular, I will discuss the connection (or lack thereof) between quenching and morphological transformation. Furthermore, I will highlight how such galaxies grow in a self-regulated equilibrium and thereby building up their central bulge component. I will show the importance of understanding the variability of the star formation rate on different timescales to constrain numerical simulation. Finally, I will end by an outlook of the key questions that we can achieve with the next generation of telescope such as the James Webb Space Telescope and the 30m-class telescopes.