Constraining f(R) gravity with a k -cut cosmic shear analysis of the Hyper Suprime-Cam first-year data

Leah Vazsonyi,Agnès Ferté,Jason Rhodes,Georgios Valogiannis,Peter L Taylor,Nesar S Ramachandra

doi:10.1103/physrevd.104.083527

Abstract

Using Subaru Hyper Suprime-Cam (HSC) year 1 data, we perform the first $k$-cut cosmic shear analysis constraining both $\Lambda$CDM and $f(R)$ Hu-Sawicki modified gravity. To generate the $f(R)$ cosmic shear theory vector, we use the matter power spectrum emulator trained on COLA (COmoving Lagrangian Acceleration) simulations. The $k$-cut method is used to significantly down-weight sensitivity to small scale ($k > 1 \ h {\rm Mpc }^{-1}$) modes in the matter power spectrum where the emulator is less accurate, while simultaneously ensuring our results are robust to baryonic feedback model uncertainty. We have also developed a test to ensure that the effects of poorly modeled small scales are nulled as intended. For $\Lambda$CDM we find $S_8 = \sigma_8 (\Omega_m / 0.3) ^ {0.5} = 0.789 ^{+0.039}_{-0.022}$, while the constraints on the $f(R)$ modified gravity parameters are prior dominated. In the future, the $k$-cut method could be used to constrain a large number of theories of gravity where computational limitations make it infeasible to model the matter power spectrum down to extremely small scales.

Highlights

Weak gravitational lensing offers a unique test of gravity on cosmological scales
The precision of these cosmological tests of gravity will increase in the coming decade thanks to large amounts of precise data coming from Stage IV experiments including Euclid1 [1], the Nancy Grace Roman Space Telescope2 [2] and the Rubin Observatory
Modeling biases are of particular concern as weak lensing is sensitive to scales down to k ∼ 10h Mpc−1 in the matter power spectrum, deep into the nonlinear regime [3]

Summary

Introduction

Weak gravitational lensing offers a unique test of gravity on cosmological scales. The precision of these cosmological tests of gravity will increase in the coming decade thanks to large amounts of precise data coming from Stage IV experiments including Euclid1 [1], the Nancy Grace Roman Space Telescope2 [2] and the Rubin Observatory.3With the improved statistical precision of these surveys, extreme care must be taken to account for and remove systematic errors which could introduce biases in the parameter inference. Weak gravitational lensing offers a unique test of gravity on cosmological scales. Modeling biases are of particular concern as weak lensing is sensitive to scales down to k ∼ 10h Mpc−1 in the matter power spectrum, deep into the nonlinear regime [3]. While it is not the primary focus of this work, the impact of baryonic feedback on these scales is highly uncertain [4]. It is not possible to do this analytically [5], but one can obtain the nonlinear power spectrum from an emulator [6,7,8] (or halo model [9]) trained (calibrated) on a suite of Oð100Þ [7] high resolution N-body simulations, run over a large volume of cosmological parameter space

Objectives

Results

Conclusion