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(NL). Considering various statistical quantities (probability distribution function, 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 vertical bar f(NL)vertical bar compatible with the present cosmic microwave background constraints and reaching at most 10-15 per cent for the most extreme cases with vertical bar f(NL)vertical bar = 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(m), finding that an error in the determination of sigma(8) (Omega(m)) of about 3 (10) per cent gives differences comparable with non-Gaussian models having f(NL) = +/- 1000. These results suggest that the possible presence of an amount of primordial non-Gaussianity corresponding to vertical bar f(NL)vertical bar = 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 by breaking the degeneracy with other cosmological parameters and using data from deep surveys covering a large fraction of the sky.

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

BRANCHINI, ENZO FRANCO;
2011

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(NL). Considering various statistical quantities (probability distribution function, 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 vertical bar f(NL)vertical bar compatible with the present cosmic microwave background constraints and reaching at most 10-15 per cent for the most extreme cases with vertical bar f(NL)vertical bar = 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(m), finding that an error in the determination of sigma(8) (Omega(m)) of about 3 (10) per cent gives differences comparable with non-Gaussian models having f(NL) = +/- 1000. These results suggest that the possible presence of an amount of primordial non-Gaussianity corresponding to vertical bar f(NL)vertical bar = 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 by breaking the degeneracy with other cosmological parameters and using data from deep surveys covering a large fraction of the sky.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11567/1071384
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