EAGLE (Evolution and Assembly of GaLaxies and their Environments) is a simulation aimed at understanding how galaxies form and evolve.  This computer calculation models the formation of structures in a cosmological volume, 100 Megaparsecs on a side (over 300 million light-years). This is large enough to contain 10,000 galaxies of the size of the Milky Way or bigger, enabling a comparison with the whole zoo of galaxies visible in the Hubble Deep field for example. This website contains downloadable images and movies, many of which are located in Highlights or Downloads.

The simulation starts when the Universe is still very uniform - no stars nor galaxies had formed yet - with cosmological parameters motivated by observations by the Planck satellite of the cosmic microwave background.  Crucial parameters are the density of dark matter - which allows structures to grow, baryonic matter - the gas from which stars form, and the cosmological constant - responsible for cosmic acceleration.

Dark matter enables structures like galaxies to form, even while the Universe is expanding rapidly. Gas falling into these dark matter structures cools and forms stars: this is how galaxies form. However core collapse supernovae, exploding massive stars, and AGN (Active Galactic Nuclei), bursting supermassive black holes, severely limit what fraction of the gas forms stars. The devastating effects of these explosions can be directly seen in starburst galaxies such as M82 and massive galaxies such as those in the Perseus cluster. Modelling these aspects accurately is key to produce a virtual universe that looks like the real one.

The image below is a slice through the simulation volume, with the intergalactic gas colour coded from blue to green to red with increasing temperature. Hot gas has temperatures of more than 100,000K, and is contained with dark matter structures that host galaxies.  Such hot gas can be detected in X-rays. The insets zoom into a galaxy like the Milky Way, showing first its gas, and then its beautiful stellar disc: it looks remarkably similar to observed spirals. 

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