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The cosmic evolution of massive black holes

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Black hole interactions with their galactic environments

Massive black holes of millions of solar masses and above populate the centres of today's galaxies, including the Milky Way. Their properties both depend on and affect the host galaxies.


The masses of black holes in local galaxies show correlations with the properties of their hosts, indicating that the growth of black holes is intimately linked to their environment. However, little is known in detail about how they form and interact with their hosts, especially in early cosmic epochs. Funded by the EU, the MBHG (The cosmic evolution of massive black holes) project undertook a theoretical investigation of the formation of massive black holes and their growth inside galaxies. For this purpose, the research team used cosmological hydrodynamical simulations and semi-analytical models. The team followed the evolution of the galaxy/black hole system from the epoch of black hole formation to today, in different types of galaxies. They studied the connection between black hole formation, the star formation history of the host and the cosmic environment. A focus was the role of environment on black hole growth, especially in the first small galaxies in early cosmic times. MBHG also investigated the evolution of massive black holes during galaxy mergers, focusing on both dynamics and accretion properties. The project explored when massive black holes light up as active galactic nuclei during galaxy mergers as well as the conditions necessary to develop binary and multiple black holes. Simulations focused on the astrophysical details using high spatial and temporal resolution, in order to track faithfully the properties of gas, stars and black holes over time. Empirical, semi-analytical and numerical approaches were used in combination to obtain the most consistent and comprehensive view possible of the joint evolution of black holes and their host galaxies. The MBHG project also provided the theoretical framework for planning future European facilities such as the Advanced Telescope for High-Energy Astrophysics (ATHENA) and the evolved Laser Interferometer Space Antenna (eLISA). Watch the project’s video here.


Black hole, galaxies, MBHG, cosmic evolution, star formation, accretion

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