Abstract
Model-independent constraints on modified gravity models hitherto exist mainly on linear scales [1]. A recently developed formalism presented a consistent parameterisation that is valid on all scales [2]. Using this approach, we perform model-independent modified gravity N-body simulations on all cosmological scales with a time-dependent μ. We present convergence tests of our simulations, and we examine how well existing fitting functions reproduce the non-linear matter power spectrum of the simulations. We find that although there is a significant variation in the accuracy of all of the fitting functions over the parameter space of our simulations, the ReACT [3] framework delivers the most consistent performance for the matter power spectrum. We comment on how this might be improved to the level required for future surveys such as Euclid and the Vera Rubin Telescope (LSST). We also show how to compute weak-lensing observables consistently from the simulated matter power spectra in our approach, and show that ReACT also performs best when fitting the weak-lensing observables. This paves the way for a full model-independent test of modified gravity using all of the data from such upcoming surveys.
Highlights
This restriction represents a significant challenge, since upcoming cosmological surveys such as Euclid 3, the Vera Rubin Observatory 4, the Nancy Roman Space Telescope 5 and the Square Kilometre Array (SKA) 6 will generate a multitude of data on non-linear cosmological scales
The key results of this paper are a presentation of the phenomenology of these simulations, an evaluation of existing fitting functions for capturing this phenomenology, and a demonstration of the application and importance of this framework for weak-lensing observables
The only fitting function calibrated from N -body simulations for the matter power spectrum on non-linear scales in phenomenological modified gravity was presented in [35]
Summary
This restriction represents a significant challenge, since upcoming cosmological surveys such as Euclid 3, the Vera Rubin Observatory 4, the Nancy Roman Space Telescope 5 and the Square Kilometre Array (SKA) 6 will generate a multitude of data on non-linear cosmological scales. A careful choice of the parameters ensures that we can run simulations characterised by a single parameter, and include the effect of the other in post-processing (see sections 2 and 5 for more details) Understanding this behaviour, and being able to capture it using fitting functions is important if we are to use this approach to analyse the data from generation surveys. These missions will generate a multitude of data, on non-linear cosmological scales.
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