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 particular, in major mergers between gas-rich disks, strong inflows
of gas into the centers of remnants can be excited, explaining the
high star formation rates inferred in ultraluminous infrared galaxies
and fueling the growth of supermassive black holes. The interplay
between black hole fueling and associated feedback effects makes these
objects briefly visible as bright optical quasars before they evolve
into passive galaxies with global properties similar to elliptical
galaxies. The relic signatures of this evolutionary process can be
seen in the light profiles of observed ellipticals, which exhibit a
two-component structure, and through correlations between supermassive
black holes and their hosts. The simulations provide a physical basis
for understanding the formation of ellipticals and demonstrate that
dissipation played a crucial role in establishing the fundamental
plane of elliptical galaxies and in determining the compact nature of
these objects at high redshifts.