Limits on Isocurvature Perturbations from Non-Gaussianity in WMAP Temperature Anisotropies

Details Limits on Isocurvature Perturbations from Non-Gaussianity in WMAP Temperature Anisotropies Limits on Isocurvature Perturbations from Non-Gaussianity in WMAP Temperature Anisotropies

2008-12-18

arxiv.org/abs/0812.3500v3

Mon.Not.Roy.Astron.Soc.398:2188-2198,2009

Astronomy and Astrophysics

Astrophysics

13 pages, 5 figures, MNRAS accepted

Scientific paper

10.1111/j.1365-2966.2009.15269.x

We study the effect of primordial isocurvature perturbations on non-Gaussian properties of CMB temperature anisotropies. We consider generic forms of the non-linearity of isocurvature perturbations which can be applied to a wide range of theoretical models. We derive analytical expressions for the bispectrum and the Minkowski Functionals for CMB temperature fluctuations to describe the non-Gaussianity from isocurvature perturbations. We find that the isocurvature non-Gaussianity in the quadratic isocurvature model, where the isocurvature perturbation S is written as a quadratic function of the Gaussian variable sigma, S=sigma^2-, can give the same signal-to-noise as f_NL=30 even if we impose the current observational limit on the fraction of isocurvature perturbations contained in the primordial power spectrum alpha. We give constraints on isocurvature non-Gaussianity from Minkowski Functionals using WMAP 5-year data. We do not find a significant signal of the isocurvature non-Gaussianity. For the quadratic isocurvature model, we obtain a stringent upper limit on the isocurvature fraction alpha<0.070 (95% CL) for a scale invariant spectrum which is comparable to the limit obtained from the power spectrum.

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