Abstract

Galaxy clusters are immersed in hot atmospheres shining X-rays. At their centres reside the largest galaxies in the universe. A significant fraction of central galaxies harbour molecular gas reservoirs exceeding 10^9 solar masses that are fuelling star formation at rates of tens of solar masses per year. New observations obtained with the Atacama Large Millimeter Array have revealed a diversity of molecular gas dynamics and morphologies including, inflow and outflow, and star formation occurring in filaments rather than in molecular disks. Molecular cloud ensemble velocities often lie far below the stellar velocity dispersions, approaching terminal rather than free-fall speeds. Observation indicates that molecular clouds are lifted by, and/or form, quickly in the wakes of buoyantly-rising radio bubbles. This mechanism may lead to circulating flows of hot and cold gas that sustains feedback in massive galaxies.