case western reserve university



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.