# C1 - Simulating the Galaxy Population of Dark Energy Universes

## Summary

The ability of DES, eBOSS, Euclid and other ongoing or planned surveys to constrain Dark Energy depends on an accurate understanding of systematic effects, such as the scale-dependent bias between the observed luminous red galaxies and the underlying matter distribution, the impact of mild non-linear evolution on the baryonic acoustic oscillations (BAOs), or the effects of galaxy outflows and reionization on Lyman-α forest spectra. Numerical simulations of the galaxy formation process are the most powerful technique to accurately quantify these effects, and are in fact indispensable to fully exploit the observational data. In this project, we aim to improve the understanding of systematic effects affecting the observational Dark Energy probes in three different ways. (1) We will carry out very large hydrodynamic Lyman-α forest simulations to characterise the relation between galaxies and the forest. Our simulations will cover an unprecedentedly large volume for simulations of this type, while at the same time resolving the forest on small scales and accurately tracking galaxy evolution and its feedback on the gas by means of new hybrid simulation technique. (2) We will develop new analysis methods for galaxy bias by combining sophisticated semi-analytic galaxy formation models with the largest and best resolved N-body simulations. Using a simulation scaling methodology, we will extend the galaxy biasing model we derive to also account for the cosmological parameter dependence and for uncertainties arising from galaxy formation physics. Finally, (3) we will investigate new ways to characterise the non-linear galaxy and Dark Matter density fields with measures of integral geometry, thereby providing an alternative approach to the use of unwieldy hierarchies of higher order correlation functions.

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