At all scales in the Universe, gravity wages a perpetual campaign to compress baryons to ever higher densities. Cosmic filaments, galaxies, interstellar clouds, and individual stars represent successive failures in the struggle against gravity. But at the bottom of the scale, stars fight back. Stellar nuclear burning creates energy, and “feedback” of this energy in various forms is essential to slowing and reversing gravitational collapse. The most important forms of stellar feedback are ultraviolet radiation and supernova blast waves. Both of these are produced by massive stars that have very short lives, and hence feedback is tightly coupled with star formation itself. The destructive effects of star formation feedback are widely seen even in popular astronomical images, but we have only recently developed the computational methods and theoretical framework that enable us to quantify and understand the physics involved. In this talk, I will describe recent modeling of three different forms of feedback at three different scales. At the smallest scale, I will show how stellar radiation from young clusters limits collapse and expels most of the gas in star-forming giant molecular clouds. At intermediate scales, I will explain how supernova blasts drive turbulence that maintains vertical equilibrium and controls star formation rates in the interstellar medium of disk galaxies like our own Milky Way. At large scales, I will argue that cosmic rays (which are accelerated by supernova shocks) may be able to propel gas out of dwarf galaxies at a higher rate than the remaining gas is locked up in stars, helping to explain why dwarfs are so baryon deficient. Each process represents a form of star formation self-regulation, and highlights different fascinating aspects of the physics of astrophysical fluids.
Host: Suzanne Staggs, Princeton University