Recent observations have delivered new insight into the structure and evolution of massive galaxies. Once thought of as relatively simple systems, it is now clear that these galaxies are diverse and can contain multiple stellar populations. Their assembly was a drawn-out process influenced both by the dark matter halos which surround them and the supermassive black holes in their cores. Many of their stars were acquired by cannibalizing smaller galaxies from a surrounding group or cluster, yet their stellar initial mass function appears to depend on the mass of the final galaxy. In addition, the growth of massive galaxies has been shaped by interaction with a reservoir of circumgalactic gas whose structure and composition is now becoming observationally accessible.
This Aspen Winter Conference will explore the richness and diversity of the evolutionary paths of massive galaxies, attempting
(i) to synthesize a coherent picture from recent observational and simulation results,
(ii) to identify major areas of continuing uncertainty, and
(iii) to formulate observational and modeling strategies to eliminate the remaining gaps in our understanding.