Emulators for the non-linear matter power spectrum beyond $\Lambda$CDM

Understand

Accurate predictions for the non-linear matter power spectrum are needed to confront theory with observations in current and near future weak lensing and galaxy clustering surveys.

• We propose a computationally cheap method to create an emulator for modified gravity models by utilizing existing emulators for $\Lambda$CDM.
• Using a suite of $N$-body simulations we construct a fitting function for the enhancement of both the linear and non-linear matter power spectrum in the commonly studied Hu-Sawicki $f(R)$ gravity model valid for wave-numbers $k \lesssim 5-10\, h\text{Mpc}^{-1}$ and redshifts $z \lesssim 3$.
• We show that the cosmology dependence of this enhancement is relatively weak so that our fit, using simulations coming from only one cosmology, can be used to get accurate predictions for other cosmological parameters.