The Theory of Galaxy Formation: Current Issues
David Weinberg, Ohio State University
I will describe what I see as the major current issues in the
theory of galaxy formation and discuss some of the insights that
come from comparing hydrodynamic simulations or analytic models
to observations. I will pay particular attention to the mechanisms
by which galaxies gain mass, the origin of bimodality in the
galaxy population, the origin of the bright-end cutoff in the
galaxy luminosity function, and the origin of disk galaxy scaling
relations. Hydrodynamic simulations show two distinct modes of
gas accretion, "hot" accretion from hydrostatic halos and "cold"
accretion along filaments, with cold accretion dominating in lower
mass systems. Explaining galaxy bimodality, the frequency of
bulge-dominated systems, and the luminosity function cutoff appears to
require a mechanism (most likely AGN feedback) that suppresses
hot accretion.
