On Mitigation of the Uncertainty in Nonlinear Matter Clustering for Cosmic Shear Tomography

TL;DR

This paper introduces a method to recover dark energy information from cosmic shear data by self-calibrating the nonlinear matter power spectrum, addressing uncertainties from baryonic effects on small scales.

Contribution

It proposes a novel self-calibration approach that marginalizes over all possible nonlinear matter power spectra to recover dark energy information in cosmic shear analysis.

Findings

Recover 90% of dark energy information through self-calibration.

Require 1% accuracy in the nonlinear matter power spectrum down to k=50 h/Mpc.

Address the challenge of baryonic effects on small-scale matter clustering.

Abstract

We present a new method that deals with the uncertainty in matter-clustering in cosmic shear power spectrum analysis that arises mainly due to poorly understood nonlinear baryonic processes on small-scales. We show that the majority of information about dark energy physics contained in the shear power comes from these small-scales; removing these nonlinear scales from a cosmic shear analysis results in a 50% cut in the accuracy of measurements of dark energy parameters, marginalizing over all other parameters. In this paper we propose a method to recover the information on small-scales by allowing cosmic shear surveys to measure the nonlinear matter power spectrum themselves and marginalize over all possible power spectra using path integrals. Information is still recoverable in these nonlinear regimes from the geometric part of weak lensing. In this self-calibration regime we find we recover 90% of the information on dark energy. Including an informative prior, we find the nonlinear matter power spectrum needs to be accurately known to 1% down to k=50 h/Mpc to recover 99% of the dark energy information. This presents a significant theoretical challenge to understand baryonic effects on the scale of galaxy haloes. However self-calibration from weak lensing may also provide observational input to help constrain baryon physics.