Probing Primordial Non-Gaussianity with Weak Lensing Minkowski Functionals

TL;DR

This paper demonstrates that Minkowski Functionals of weak lensing maps can effectively constrain primordial non-Gaussianity and dark energy parameters, with forecasts for upcoming large surveys showing promising precision improvements.

Contribution

It introduces a method to use Minkowski Functionals of weak lensing maps for constraining primordial non-Gaussianity and cosmological parameters, supported by simulations and Fisher analysis.

Findings

Weak lensing Minkowski Functionals can constrain f_NL to ~80 for 1500 deg^2 surveys.

Future surveys like LSST could constrain f_NL to ~25 with Minkowski Functionals.

Tomographic analysis improves constraints by utilizing multiple redshift bins.

Abstract

We study the cosmological information contained in the Minkowski Functionals (MFs) of weak gravitational lensing convergence maps. We show that the MFs provide strong constraints on the local type primordial non-Gaussianity parameter f_NL. We run a set of cosmological N-body simulations and perform ray-tracing simulations of weak lensing, to generate 100 independent convergence maps of 25 deg^2 field-of-view for f_NL = -100, 0 and 100. We perform a Fisher analysis to study the degeneracy among other cosmological parameters such as the dark energy equation of state parameter w and the fluctuation amplitude sigma_8. We use fully nonlinear covariance matrices evaluated from 1000 ray-tracing simulations. For the upcoming wide-field observations such as Subaru Hyper Suprime-Cam survey with the proposed survey area of 1500 deg^2, the primordial non-Gaussianity can be constrained with a level of f_NL ~ 80 and w ~ 0.036 by weak lensing MFs. If simply scaled by the effective survey area, a 20000 deg^2 lensing survey using Large Synoptic Survey Telescope will give constraints of f_NL ~ 25 and w ~ 0.013. We show that these constraints can be further improved by a tomographic method using source galaxies in multiple redshift bins.