In Search of a Unified Picture for Galaxy Evolution

Lars Hernquist, Harvard University

Traditionally, it has been thought that elliptical galaxies originated primarily in a dissipationless manner, because these objects are deficient in gas relative to spirals and are spheroidal in shape, unlike galaxies with thin disks. Within the context of the merger hypothesis for the formation of ellipticals, it has long been recognized that mergers between pure stellar disks with properties similar to those of nearby galaxies cannot account for the high phase space densities of ellipticals. In this talk, I describe simulations exploring the consequences of dissipation in building elliptical galaxies through mergers and signatures of this process in their observed properties. In addition, I describe consequences of this process for our understanding of the origin of starburst and ultraluminous infrared galaxies, quasars, and supermassive black holes.