Stellar Populations and the Structural Evolution of Galaxies

Synopsis

It is well established that galaxies are divided into those that are star-forming and those that have stopped forming stars long ago.  The cessation of star formation in galaxies ("quenching") correlates strongly with galaxy structural properties, but the physical reasons remain disputed.  I will discuss issues of correlation and causation, and highlight evidence from observational surveys, hydrodynamical simulations and machine learning that point to multiple evolutionary pathways along which galaxies both grow and die.