Star formation in a cooling flow

The central galaxies in some clusters are observed to accrete cooling intracluster gas at rates of between 4 and 300 M⊙yr−1. The colors and luminosities of these galaxies show evidence for star formation at less than 10 per cent of those rates, if the stellar initial-mass-function is similar to that in the solar neighborhood. We show that the high-pressure dust-free environment in the cooling flow lowers the Jeans mass and thereby favors the formation of lower-mass stars. The lack of detectable H I in most of these clusters is also explained.