High-accuracy power spectra including baryonic physics in dynamical Dark Energy models

Abstract

The next generation mass probes will obtain information on non-linear power spectra P(k, z) and their evolution, allowing us to investigate the nature of Dark Energy. To exploit such data we need high-precision simulations, extending at least up to scales of k≃ 10 h Mpc−1, where the effects of baryons can no longer be neglected. In this paper, we present a series of large scale hydrodynamical simulations for ΛCDM and dynamical Dark Energy (dDE) models, in which the equation of state parameter is z dependent. The simulations include gas cooling, star formation and Supernovae feedback. They closely approximate the observed star formation rate and the observationally derived star/Dark Matter mass ratio in collapsed systems. Baryon dynamics cause spectral shifts exceeding 1 per cent at k > 2–3 h Mpc−1 compared to pure N-body simulations in the ΛCDM simulations. This agrees with previous studies, although we find a smaller effect (∼50 per cent) on the power spectrum amplitude at higher k values. dDE exhibits similar behaviour, even though the dDE simulations produce ∼20 per cent less stars than the analogous ΛCDM cosmologies. Finally, we show that the technique introduced in Casarini et al. to obtain spectra for any w(z) cosmology from constant-w models at any redshift still holds when gas physics is taken into account. While this relieves the need to explore the entire functional space of DE state equations, we illustrate a severe risk that future data analysis could lead to misinterpretation of the DE state equation.