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The Feedback Acting on Baryons in Large-scale Environments (FABLE) simulations follow the formation and evolution of galaxies across a diverse range of environments; from the sparsely-populated field environment to small groups of just a handful of galaxies to rich clusters containing hundreds of member galaxies. Each simulation in the FABLE suite evolves a patch of a mock universe from shortly after the Big Bang to the present-day using the state-of-the-art numerical code AREPO, which incorporates a comprehensive set of models for the physical processes that drive galaxy formation. Our diverse array of high-resolution simulations have been performed on DiRAC high-performance computing facilities and required several million CPU hours to complete. The FABLE simulations simultaneously produce realistic galaxies, groups and clusters, which allows us to explore in detail the astrophysical processes at play on this vast range of scales with the ultimate goal of constraining the cosmology of our Universe to a high precision from the wealth of upcoming observations of galaxy groups and clusters.

The video above shows the evolution of one of the most massive FABLE clusters over the past 13.8 billion years. Here we are viewing the evolution of the gas in a large region centred on the forming cluster in which the brightness and colour correspond to the density and temperature of the gas. At early times we see the formation of the basic structure of the `Cosmic Web' in the form of sheets and filaments and the voids in between them. The densest regions lie at the intersections of these filaments and collapse under gravity to form massive halos containing large amounts of dense, hot gas. These structures continue to grow by mergers with each other and by accretion of lower density gas from the surrounding regions. As the gas is compressed by gravity it is heated to very high temperatures, changing colour from blue to green to white. By the present-day these structures have coalesced into a massive galaxy cluster 17 million light-years in diameter, weighing a million billion times the mass of the Sun and hosting hundreds of member galaxies.

KICC Annual Report 2018

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