Galaxy evolution is governed by feedback mechanisms that seem to be self-regulating. In galaxy clusters, feedback heating appears to balance radiative cooling, but in smaller halos, the energy input from feedback exceeds radiative cooling and causes the atmospheres of those halos to expand. To measure the total amount of feedback energy input we therefore need to map the baryons associated with halos on scales larger than the virial radius, which is hard to do but essential for understanding how feedback energy regulates a galaxy's gas supply.