A numerical study of the effects of primordial non-Gaussianities on weak lensing statistics

Abstract

While usually cosmological initial conditions are assumed to be Gaussian, inflationary theories can predict a certain amount of primordial non-Gaussianity which can have an impact on the statistical properties of the lensing observables. In order to evaluate this effect, we build a large set of realistic maps of different lensing quantities starting from light-cones extracted from large dark-matter only N-body simulations with initial conditions corresponding to different levels of primordial local non-Gaussianity strength $f_{\mathrm{NL}}$. Considering various statistical quantities (PDF, power spectrum, shear in aperture, skewness and bispectrum) we find that the effect produced by the presence of primordial non-Gaussianity is relatively small, being of the order of few per cent for values of $|f_{\mathrm{NL}}|$ compatible with the present CMB constraints and reaching at most 10-15 per cent for the most extreme cases with $|f_{\mathrm{NL}}|=1000$. We also discuss the degeneracy of this effect with the uncertainties due to the power spectrum normalization ${\sigma }_8$ and matter density parameter ${\Omega }_{\mathrm{m}}$, finding that an error in the determination of ${\sigma }_8$ (${\Omega }_{\mathrm{m}}$) of about 3 (10) per cent gives differences comparable with non-Gaussian models having $f_{\mathrm{NL}}=\pm 1000$. These results suggest that the possible presence of an amount of primordial non-Gaussianity corresponding to $|f_{\mathrm{NL}}|=100$ is not hampering a robust determination of the main cosmological parameters in present and future weak lensing surveys, while a positive detection of deviations from the Gaussian hypothesis is possible only breaking the degeneracy with other cosmological parameters and using data from deep surveys covering a large fraction of the sky.

accepted by MNRAS

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