Sigma-eight at the percent level: the EFT likelihood in real space

Fabian Schmidt

doi:10.1088/1475-7516/2021/04/032

Abstract

The effective field theory likelihood for the density field of biased tracers allows for cosmology inference from the clustering of galaxies that consistently uses all available information at a given order in perturbation theory. This paper presents results and implementation details on the real-space (as opposed to Fourier-space) formulation of the likelihood, which allows for the incorporation of survey window functions. The implementation further uses a Lagrangian forward model for biased tracers which automatically accounts for all relevant contributions up to any desired order. Unbiased inference of σ8 is demonstrated at the 2% level for cutoff values Ł ≲ 0.14 h Mpc-1 for halo samples over a range of masses and redshifts. The inferred value shows the expected convergence to the ground truth in the low-cutoff limit. Apart from the possibility of including observational effects, this represents further substantial improvement over previous results based on the EFT likelihood.

Highlights

ArXiv ePrint: 2009.14176 factor, and σ8, allowing for interesting additional tests of the ΛCDM paradigm and possibly improved constraints on the sum of neutrino masses
A new approach to extracting the nonlinear information, which is only marginally accessed by the power spectrum, has recently gathered increased attention: Loosely referred to as forward modeling, this approach proceeds by writing down a likelihood for the entire galaxy density field, and performing a full joint Bayesian inference of cosmological parameters along with the phases of the initial conditions corresponding to the observed survey volume [15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32]
Unbiased inference corresponds to values of Ain that are consistent with 1 within errors

Summary

Introduction

ArXiv ePrint: 2009.14176 factor, and σ8, allowing for interesting additional tests of the ΛCDM paradigm and possibly improved constraints on the sum of neutrino masses. Unbiased inference of σ8 (equivale√nt, when all remaining cosmological parameters are fixed, to the primordial normalization As) was demonstrated at the 4–8% level depending on halo mass and redshift In this test, the phases of the forward model were fixed to the truth, i.e. the initial conditions used in the N-body simulations. The constraint on σ8 is not obtainable using linear theory due to the bias-amplitude degeneracy, and so is exclusively due to the robust extraction of nonlinear information These results were based on a Fourier-space formulation of the EFT likelihood. [39], this formulation allows for an incorporation of the most important corrections to the leading EFT likelihood, a Gaussian with constant diagonal noise, in particular the modulation of the noise by long-wavelength modes, or equivalently the stochasticity of the bias parameters This formulation permits one to include the survey window function in a computationally efficient way.

Results

Discussion

Conclusion