Journal Article

A weak lensing view on primordial non-Gaussianities

Björn Malte Schäfer, Alessandra Grassi, Mischa Gerstenlauer and Christian T. Byrnes

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 421, issue 1, pages 797-807
Published in print March 2012 | ISSN: 0035-8711
Published online March 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.20357.x
A weak lensing view on primordial non-Gaussianities

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We investigate the signature of primordial non-Gaussianities in the weak lensing bispectrum, in particular the signals generated by local, orthogonal and equilateral non-Gaussianities. The questions we address include the signal-to-noise ratio generated in the Euclid weak lensing survey (we find that the 1σ errors for fNL are 200, 575 and 1628 for local, orthogonal and equilateral non-Gaussianities, respectively), mis-estimations of fNL if one chooses the wrong non-Gaussianity model (mis-estimations by up to a factor of ±3 in fNL are possible, depending on the choice of the model), the probability of noticing such a mistake (improbably large values for the χ2-functional occur from fNL∼ 200 onwards), degeneracies of the primordial bispectrum with other cosmological parameters (only the matter density Ωm plays a significant role), and the subtraction of the much larger, structure formation generated bispectrum. If a prior on a standard cold dark matter parameter set including the dark energy equation of state w is available from Euclid and Planck, the structure formation bispectrum can be predicted accurately enough for subtraction, and any residual structure formation bispectrum would influence the estimation of fNL to a minor degree. Configuration space integrations which appear in the evaluation of χ2-functionals and related quantities can be carried out very efficiently with Monte Carlo techniques, which reduce the complexity by a factor of while delivering sub-per cent accuracies. Weak lensing probes smaller scales than the cosmic microwave background (CMB) and hence provides an additional constraint on non-Gaussianities, even though they are not as sensitive to primordial non-Gaussianities as the CMB.

Keywords: gravitational lensing: weak; methods: analytical; large-scale structure of Universe

Journal Article.  6794 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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