Fundamentals of Gaseous Halos

Coordinators: Cameron Hummels, Ben Oppenheimer, Mark Voit, and Jess Werk

Gas in the halos of galaxies dominates the universe's baryon budget, traces its dark-matter potential wells, and supplies the fuel for star formation. Circumgalactic gas has also long been suspected to regulate galaxy evolution by warehousing the byproducts of galactic metabolism and recycling them through galaxies. Many elementary questions about the circumgalactic medium (CGM) remain unanswered because it has been so difficult to detect, but within the last decade observations have begun to reveal its contents, dynamics, and thermal structure. Those measurements, in turn, are revolutionizing our theoretical understanding of how galaxies obtain fresh gas for star formation, how supernova explosions collectively drive powerful outflows from galaxies, how thermal instability and precipitation regulate the structure of the CGM, and how feedback processes may suppress the flow of gas into the galaxy.

This program will bring together specialists from the numerous, disparate communities of observers and theorists whose research intersects with the CGM. One of the primary goals will be to assemble a coherent theoretical framework for interpreting the diverse array of CGM observations that are now becoming available.