Probing primordial non-gaussianity with weak-lensing minkowski functionals

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 fNL. We run a set of cosmological N-body simulations and perform ray-tracing simulations of weak lensing to generate 100 independent convergence maps of a 25deg2 field of view for fNL = -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 σ8. We use fully nonlinear covariance matrices evaluated from 1000 ray-tracing simulations. For upcoming wide-field observations such as those from the Subaru Hyper Suprime-Cam survey with a proposed survey area of 1500deg2, the primordial non-Gaussianity can be constrained with a level of fNL ∼ 80 and w ∼ 0.036 by weak-lensing MFs. If simply scaled by the effective survey area, a 20,000deg2 lensing survey using the Large Synoptic Survey Telescope will yield 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. © 2012. The American Astronomical Society. All rights reserved.