Black holes regulate cool gas accretion in massive galaxies

Abstract

The nucleus of almost all massive galaxies contains a supermassive black hole (BH)¹. The feedback from the accretion of these BHs is often considered to have crucial roles in establishing the quiescence of massive galaxies^2-14, although some recent studies show that even galaxies hosting the most active BHs do not exhibit a reduction in their molecular gas reservoirs or star formation rates^15-17. Therefore, the influence of BHs on galaxy star formation remains highly debated and lacks direct evidence. Here, based on a large sample of nearby galaxies with measurements of masses of both BHs and atomic hydrogen (HI), the main component of the interstellar medium¹⁸, we show that the HI gas mass to stellar masses ratio (μ_HI = M_HI/M_⋆) is more strongly correlated with BH masses (M_BH) than with any other galaxy parameters, including stellar mass, stellar mass surface density and bulge masses. Moreover, once the μ_HI-M_BH correlation is considered, μ_HI loses dependence on other galactic parameters, demonstrating that M_BH serves as the primary driver of μ_HI. These findings provide important evidence for how the accumulated energy from BH accretion regulates the cool gas content in galaxies, by ejecting interstellar medium gas and/or suppressing gas cooling from the circumgalactic medium.