Astronomy Colloquium

Galaxies must continuously accrete gas from the intergalactic medium in order to maintain their star formation rates. At the same time, star-forming galaxies and their black holes drive powerful winds that strongly affect their evolution. Inflows and outflows are thus among the key physical processes in galaxy formation, tying together the vastly different scales involved. I will first summarize the inflow predictions from cosmological simulations and show how they can be tested observationally. In doing so, I will address the physical nature of Ly-alpha blobs and Lyman limit absorbers. Motivated by breakthrough discoveries of massive, galaxy-scale outflows driven by active galactic nuclei in the last year, I will then address two puzzles raised by the data: the extreme multiphase structure traced by cool absorbers, and the origin of the large outflow momentum fluxes. The talk will conclude by outlining advances that will dramatically improve the realism and predictive power of theoretical studies of galaxy formation in the next few years.