An accurate halo model for fitting non-linear cosmological power spectra and baryonic feedback models

TL;DR

This paper introduces an optimized halo model that accurately predicts non-linear matter power spectra across various cosmologies and incorporates baryonic feedback effects, aiding future weak lensing analyses.

Contribution

The authors develop a physically motivated, adaptable halo model fitted to simulations, achieving high accuracy and including baryonic feedback effects with minimal free parameters.

Findings

Achieves ~5% accuracy for power spectra up to k=10h/Mpc and z=2.

Successfully models baryonic feedback with only two free parameters.

Provides code for calculating power spectra using the new model.

Abstract

We present an optimized variant of the halo model, designed to produce accurate matter power spectra well into the non-linear regime for a wide range of cosmological models. To do this, we introduce physically motivated free parameters into the halo-model formalism and fit these to data from high-resolution $N$-body simulations. For a variety of $\Lambda$CDM and $w$CDM models the halo-model power is accurate to $\simeq 5$ per cent for $k\leq 10h\,\mathrm{Mpc}$ and $z\leq 2$. An advantage of our new halo model is that it can be adapted to account for the effects of baryonic feedback on the power spectrum. We demonstrate this by fitting the halo model to power spectra from the OWLS hydrodynamical simulation suite via parameters that govern halo internal structure. We are able to fit all feedback models investigated at the 5 per cent level using only two free parameters, and we place limits on the range of these halo parameters for feedback models investigated by the OWLS simulations. Accurate predictions to high-$k$ are vital for weak lensing surveys, and these halo parameters could be considered nuisance parameters to marginalize over in future analyses to mitigate uncertainty regarding the details of feedback. Finally, we investigate how lensing observables predicted by our model compare to those from simulations and from HALOFIT for a range of $k$-cuts and feedback models and quantify the angular scales at which these effects become important. Code to calculate power spectra from the model presented in this paper can be found at https://github.com/alexander-mead/hmcode