Why do some massive galaxies burn out their gas so quickly?

Observations of three massive central galaxies at intermediate redshift reveal a stark dichotomy: one contains 30 billion solar masses of molecular gas, while two others have almost none, despite all three actively forming stars. Gas depletion timescales of 0.5–1.5 billion years suggest that environmental processing in galaxy groups efficiently strips away the cold fuel needed for star formation, potentially explaining how massive galaxies transition from star-forming to dormant.