The EAGLE simulation project is a Virgo flagship program aimed at creating hi-fidelity hydrodynamic simulations of the galaxy population. It has been a major investment of intellectual effort, manpower and computing resources, with game-changing results, opening a window on the role and physics of baryons in the Universe.
EAGLE uses the latest developments in SPH techniques, with state of the art modelling of sub-grid processes such as star formation, feedback and black hole accretion. Unlike previous projects, our feedback scheme does not involve “de-coupling” feedback particles from hydrodynamic forces, or artificially suppressing cooling. The largest simulation, with a volume of 106 Mpc contains 1000s of well-resolved galaxies similar to the Milky Way and100s of galaxy groups and a handful of galaxy clusters. This huge statistical sample allows us to understand the variety of galaxy formation histories, the impact of galaxy environment and to study rare objects such as highly star forming sub-mm galaxies.
Obviously, a simulation of this size is of no use unless it is able to accurately reproduce the properties of the local galaxy population. EAGLE has been spectacularly successful: for example, the model correctly predicts the evolution of the galaxy mass function and the rising trend of galaxy specific star formation rates (Schaye et al. 2014 at z=0, Furlong et al. 2014 showing predictions at higher z). Numerous papers are in advanced stages of preparation comparing additional galaxy properties, such as HI mass functions (Bahe et al), galaxy colour distributions and luminosity functions (Trayford et al), OVI absorbers (Rahmati et al), AGN luminosity functions (Rosas-Guevara et al). The fidelity of the simulation also makes it a powerful tool for understanding the biases in observational surveys.
Having shown that the simulation’s fidelity is excellent, we can now exploit it as a tool for understanding the physical mechanisms by which galaxies form and evolve. The image above is a slice through the simulation volume, with the intergalactic gas colour coded from blue to green to red with increasing temperature. The inset images show details in a small region of the simulation centred on a spiral galaxy seen face-on.