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.

Fig. 1. Comparison between the relations of μ_HI to M_⋆ and μ_HI to M_BH for the BH sample.

a,b, μ_HI–M_⋆ (a) and μ_HI–M_BH (b) correlations. Galaxies are colour-coded by their morphological T types, with smaller values being more early-type and larger values more late-type morphologies. The orange lines represent the best-fitted linear relation, taking into account the uncertainties of both variables. c,d, Comparison of the partial correlation of μ_HI–M_⋆ (while controlling for M_BH) (c) and μ_HI–M_BH (while controlling for M_⋆) (d). The x- and y-axes show the residual in μ_HI and M_⋆ after removing their dependence on M_BH in the left panel, and M_BH after removing their dependence on M_⋆ in the right panel: Δlog μ_HI = log μ_HI − log μ_HI(M_BH) and Δlog M_⋆ = log M_⋆ − log M_⋆(M_BH) in the left panel, and Δlog μ_HI = log μ_HI − log μ_HI(M_⋆) and Δlog M_BH = log M_BH − log M_BH(M_⋆) in the right panel. The horizontal dashed line indicates zero correlation, that is, there is no intrinsic correlation between the two quantities. The Spearman correlation coefficients between the two corresponding variables are shown in each panel. The error bars refer to 1σ measurement errors.

Fig. 2. Comparison between the relations of μ_HI to M_⋆ and μ_HI to M_BH for the galaxy sample.

a,b, μ_HI–M_⋆ (a) and μ_HI–M_BH (b) correlations. Galaxies are divided into early- and late-type galaxies based on their Sérsic indexes (separated at n = 2), which are shown in red and blue contours, respectively. The HI-detection rates of galaxies are shown as a function of stellar masses and BH masses. The vertical dashed lines indicate the position when the HI-detection fraction reaches 60%. c,d, μ_HI–M_⋆ (c) and μ_HI–M_BH (d) relations. The best-fitted relations for the HI-detected galaxy sample and the BH sample are shown by the black and orange lines, respectively. We also show the μ_HI–M_BH relation for the full galaxy sample with the magenta line in d. e,f, The partial correlation between μ_HI and M_⋆ while controlling for M_BH (e), and the partial correlation between μ_HI and M_BH while controlling for M_⋆ (f). The corresponding Spearman coefficients are shown in each panel. The median 1σ error bars for the galaxy sample are shown in c and d.

Fig. 3. The impact of M_BH on the correlation between μ_HI and other main galactic parameters.

a–e, The HI-detection fraction along M_BH (a) and some other main physical parameters of galaxies, including M_⋆ (b), Σ_star (c), M_bulge (d) and SSFR (e). The vertical dashed lines indicate the position at which the HI-detection rates hit 60%. f–j, The relation between the parameters M_BH (f), M_⋆ (g), Σ_star (h), M_bulge (i) and SSFR (j) and μ_HI. The contours denote the distribution of the HI-detected galaxy sample, whereas the filled red circles denote the BH sample with 1σ error bars. The best-fitted μ_HI–M_BH relations for the HI-detected galaxy sample and the BH sample are shown in f by the black and orange lines, respectively. The median 1σ error bars for the galaxy sample are shown. k–n, The relation between the residual in μ_HI and the residual in other galactic parameters after removing their dependence on M_BH: Δlog μ_HI = log μ_HI − log μ_HI(M_BH) and Δlog X = log X − log X(M_BH) with X representing M_⋆ (k), Σ_star (l), M_bulge (m) and SSFR (n), and μ_HI(M_BH) and X(M_BH) derived from their best-fitted relation with M_BH (Extended Data Fig. 2). The solid medium-blue lines in k–n show the running median of the residuals in μ_HI. The Spearman correlation coefficients for the HI-detected galaxy sample between the corresponding x and y variables are shown in f–n.

Fig. 4. Schematic of the proposed scenario on how BHs regulate cool gas content in galaxies.

The large arrow indicates the μ_HI–M_BH correlation. The background colour scale indicates the quiescent galaxy fraction as a function of M_BH, which shows a sharp increase at M_BH ≳ 10^7.5M_⊙ (Methods and Extended Data Fig. 5), corresponding to μ_HI < 10%. At fixed M_BH, galaxies could maintain their μ_HI at a certain level determined by the relative strength of the inner halo binding energy and M_BH. Once gas accretion is enhanced onto galaxies (and their BHs), which increases μ_HI, M_BH will also grow and release additional heating energy that prevents further gas cooling or accretion. This will bring down μ_HI together with increasing M_⋆ by star formation and reach a balance at higher M_BH. Although the same process takes place in both SFGs and quiescent galaxies, the growth of M_BH or M_⋆ should be much less significant in quiescent galaxies than in SFGs, and the large range of M_BH among quiescent galaxies (M_BH ~ 10⁷⁻¹⁰M_⊙) is probably inherited from their different star-forming progenitors when they were quenched.

Extended Data Fig. 1. The impact of inclinations on the observed HI line width.

The relation between M_⋆ and the observed HI line width are shown in panels (a, c), while the relation between M_⋆ and the inclination-corrected HI line width are shown in panels(b, d), for MaNGA and xGASS galaxies respectively. The error bars refer to 1-σ errors for logM_⋆. For W₅₀, we denote 20% measurement uncertainties.

Extended Data Fig. 2. The relation between BH masses and other major galactic parameters for the BH and galaxy sample.

The relation between M_BH and M_⋆, Σ_star, M_bulge, and SSFR for the BH sample (red filled dots) and the full galaxy sample (blue contours) are shown in Panels a, b, c, and d, respectively. The best-fitted relation for the galaxy sample, the full galaxy, and the HI-detected galaxy sample are respectively drawn in solid orange, darkviolet, and black lines in each panel. These relations are used to derive the residuals of the corresponding galactic parameters after controlling for M_BH in the bottom row of Fig. 3, and Extended Data Fig. 3. The median error of the galaxy sample is shown in the upper right in each panel. The error bars refer to 1-σ errors.

Extended Data Fig. 3. The impact of M_BH on the correlation between μ_HI and other major galactic parameters for the full galaxy sample.

Similar as Fig. 3, but with the third row replaced by the relation between the residual in μ_HI and other galactic parameters after removing their dependence on M_BH based on the full sample instead of only the HI-detected ones. The solid medium-blue lines denote the running median of the residuals in μ_HI. Since the HI-detected samples are always biased compared to the full sample, the running medians exhibits a positive offset compared to zero values(black dashed lines). The median error of the galaxy sample is shown in the lower left in panel (f ~ j). The error bars refer to 1-σ errors. In the top-right corners of the middle and bottom panels, we show the Spearman correlation coefficients for the HI-detected galaxy sample between the corresponding x and y variables.

Extended Data Fig. 4. Comparison between the relations of BH masses to the HI gas fraction and to the total gas fraction.

The relation between M_BH and HI gas fraction is shown in panel a, and the relation between M_BH and total gas fraction is shown in panel b for central galaxies. The blue circles and red squares denote respectively star-forming and quiescent galaxies, which are classified based on their SSFR. Spearman correlation coefficients and the RMS between data and the fitted relations (black dashed lines) are shown in the top-right corners. The error bars refer to 1-σ errors.

Extended Data Fig. 5. Relation between SSFR and BH masses for SDSS group central galaxies.

Density map of SDSS group central galaxies is shown in the SSFR-M_BH plot. The dashed line denotes the quiescent fraction as a function of M_BH. The contours and corresponding numbers denote the galaxy number for each pixel.

Extended Data Fig. 6. The comparison between the stellar masses derived from SED-fitting and those derived based on K-band luminosities.

The SED-based estimation M_⋆ is taken from the MPA-JHU catalog and the K-band luminosity based estimation of M_⋆ is derived from the relation among M_⋆, L_K and R_e given by Ref. . The dashed line denotes the ‘1:1’ line shifted by the mean mass difference of 0.32 dex. The error bars refer to 1-σ error.