ALMA Observations of Molecular Gas in Central Cluster Galaxies

Central galaxies in groups and clusters are often rich in molecular gas. At levels upward of 10^10 Solar masses, molecular gas is linked to cooling of the host cluster's hot atmosphere. ALMA has imaged nearly a dozen systems, revealing molecular gas flows (inflow/outflow) tens of kpc in size involving masses upward of 10^10 solar masses. The flows are likely powered by radio AGN. Their flow speeds lie well below escape speeds, likely leading to molecular fountains. Molecular gas disks are rare. Narrow velocity widths of molecular cloud complexes suggest the clouds are unrelaxed and have formed recently, perhaps from low-entropy, atmospheric gas lifted behind rising radio bubbles. We show that the atmospheric conditions conducive to molecular cloud formation in centrals extend to normal ellipticals and early spirals.