The Impact of Feedback on Star and Galaxy Formation

After several decades of theoretical developments and spectacular observations of star formation sites and star forming galaxies, our understanding of star formation in the universe has profoundly evolved. Designing a theory for star formation based on physical first principles is now within our grasp, but to reach this goal we must grapple with the central  role feedback processes from young stars play in regulating star formation in galaxies and in determining the properties of newly born stellar populations deep inside molecular clouds. Modeling feedback processes such as radiation from young stars, stellar winds and ultimately explosive events like supernovae is very challenging. The relative importance of different forms of feedback energy (thermal energy, ionizing and continuum radiation, cosmic rays,  kinetic energy in jets) is still under debate, and the energy injection often occurs at very small scales that are poorly resolved by computer simulations or telescope imaging. Moreover, this energy also couples to very large scales, driving turbulence within the ISM and powering the ejection of powerful galactic winds, both of which contribute to regulating the global star formation efficiency into disk galaxies.

The goal of this conference, the kick-off meeting for our program on the physics of star formation feedback, is to set the scene for the three following months in Santa Barbara.  Focus areas will include discussion of the detailed nature and efficacy of various stellar feedback mechanisms, new theoretical and observational developments on how feedback regulates star formation at a range of scales, and inter-comparisons of numerical methods for implementing feedback in molecular clouds and in galaxies. During the week, various sessions will be dedicated to discuss critical areas where new developments  and new collaborations are needed. For example, observations of large scale gas motions within the Galaxy will be used to set constraints on theoretical and numerical models of the galactic fountain,  while detailed post-processing of computer simulations could be used by observers to infer the physical  properties of stellar outflows. Interactions between theorists and observers, and between experts in small scale and  large scale phenomenon, will shed some light on the role of these feedback processes for regulating star formation.