On mitigation of the uncertainty in non-linear matter clustering for cosmic shear tomography

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 non-linear baryonic processes on small scales. We show that the majority of information about new physics contained in the shear power comes from these small scales. Removing these non-linear scales from a cosmic shear analysis results in 50 per cent 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 non-linear matter power spectrum themselves and marginalize over all possible power spectra using path integrals. Information is still recoverable in these non-linear regimes from the geometric part of weak lensing. In this self-calibration regime we recover 90 per cent of the information on dark energy. Including an informative prior, we find that the non-linear matter power spectrum needs to be accurately known to 1 per cent down to k= 50 h−1 Mpc, or a scale of 120 kpc, to recover 99 per cent of the dark energy information. This presents a significant theoretical challenge to understand baryonic effects on the scale of galaxy haloes.