Institute for Advanced Study/Princeton University Joint Astrophysics Colloquium

Most of the baryons associated with galaxy halos reside in thecircumgalactic medium. A significant fraction of the mass is attemperatures well below the halo virial temperature. What holdsthe cool CGM up? I will present new measurements of the kinematicsof circumgalactic gas. The data show that much of the low-ionizationCGM rotates in the same direction as the galactic disk, suggestingsubstantial centrifugal support. Disturbances from galactic windsare also apparent, and I will discuss the empirical constraints onboth gas outflows and inflows. Understanding the hydrodynamics ofthe CGM is important because this physics shapes the growth ofgalactic disks.