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Direct formation of supermassive black holes via multi-scale gas inflows in galaxy mergers


Observations of distant quasars indicate that supermassive black holes of billions of solar masses already existed less than a billion years after the Big Bang1. Models in which the ‘seeds’ of such black holes form by the collapse of primordial metal-free stars2,3 cannot explain the rapid appearance of these supermassive black holes because gas accretion is not sufficiently efficient4,5,6. Alternatively, these black holes may form by direct collapse of gas within isolated protogalaxies7,8, but current models require idealized conditions, such as metal-free gas, to prevent cooling and star formation from consuming the gas reservoir9,10,11. Here we report simulations showing that mergers between massive protogalaxies naturally produce the conditions for direct collapse into a supermassive black hole with no need to suppress cooling and star formation. Merger-driven gas inflows give rise to an unstable, massive nuclear gas disk of a few billion solar masses, which funnels more than 108 solar masses of gas to a sub-parsec-scale gas cloud in only 100,000 years. The cloud undergoes gravitational collapse, which eventually leads to the formation of a massive black hole. The black hole can subsequently grow to a billion solar masses on timescales of about 108 years by accreting gas from the surrounding disk.

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Figure 1: Time evolution of the nuclear gas disk from its formation until the onset of central collapse.
Figure 2: Evolution of the mass distribution of the nuclear region.


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We thank M. Colpi, R. Durisen, F. Governato, P. Madau, T. Quinn, M. Volonteri, D. Weinberg, R. Teyssier and S. White for discussions. This research has been supported by the Swiss National Science Foundation (SNF), by the Center for Cosmology and Astro Particle Physics (CCAPP) at Ohio State University, and by the Kavli Institute for Particle Astrophysics (KIPAC) at Stanford University. L.M., S.K. and S.C. acknowledge the Kavli Institute for Theoretical Physics at the University of California in Santa Barbara (KITP) for hospitality during the initial stages of this work on the “Building the Milky Way” programme. L.M. also thanks the KITP for hospitality during the final completion of the article while on the “Exoplanets Rising” programme. All computations were performed on the Zbox3 supercomputer at the University of Zürich and on the Brutus cluster at ETH Zürich.

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L.M. provided the scientific leadership, led the design of the numerical experiments, wrote the paper and led the analysis and interpretation of the simulations. S.K. and A.E. contributed to the initial concept of the numerical experiments and to their analysis and interpretation. They also helped with the writing of the paper. S.C. performed some of the additional experiments described in the Supplementary Information, and carried out important parts of the analysis. S.C. also helped substantially with understanding the results of the mass dependence of the inflow process as well as with the writing of the final version of this Letter.

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Correspondence to L. Mayer.

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This file contains Supplementary Information comprising Supplementary Methods, and Data, Supplementary Figures 1-5 with legends and References. (PDF 1116 kb)

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Mayer, L., Kazantzidis, S., Escala, A. et al. Direct formation of supermassive black holes via multi-scale gas inflows in galaxy mergers. Nature 466, 1082–1084 (2010).

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