Place: 4421 Sterling Hall (Coffee and Cookies at 3:30 PM)
Speaker: Professor Eve Ostriker , Princeton University
Abstract: Recent years have seen significant progress in quantifying the physics of star formation feedback and its effects on the ISM within galactic disks. In this talk, I will discuss theory and numerical hydrodynamic simulations that explain and demonstrate how self-regulation is achieved through a set of balances: heating and cooling, turbulent driving and dissipation, and gravitational compaction and pressure support. Because the sources of momentum and energy are directly associated with massive star formation, the requirement of equilibrium leads to a prediction for the star formation rate. The thermal/dynamical equilibrium theory also yields predictions for the ratio of thermal to turbulent pressure, and for the proportion of warm to cold gas in the diffuse atomic ISM. Although we find that radiation feedback can be important within individual star-forming clouds, supernovae play the dominant role in the ISM overall, because the momentum injected by Sedov-Taylor blast waves is an order of magnitude greater than other source terms. Resolved simulations show that radiative supernova remnants inject a momentum ~ 1-4 e5 Msun km/s to the ISM, insensitive to the local gas properties. This momentum yield, combined with the heating rate from FUV, is just what is required to explain observed large-scale ISM properties and star formation rates.