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

Abstract

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-<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.

13 pages, 5 figures, MNRAS accepted

References in corpus (14)

• Detection of primordial non-Gaussianity (fNL) in the WMAP 3-year data at above 99.5% confidence
• Non-Gaussianity in the modulated reheating scenario
• Primordial Curvature Fluctuation and Its Non-Gaussianity in Models with Modulated Reheating
• Primordial fluctuations and non-Gaussianities in multi-field DBI inflation
• Non-Gaussianity, Spectral Index and Tensor Modes in Mixed Inflaton and Curvaton Models
• Multi-brid inflation and non-Gaussianity
• Non-Gaussianities in New Ekpyrotic Cosmology
• Large non-Gaussianity from multi-brid inflation
• The curvature perturbation in a box
• Large Non-Gaussianity Implication for Curvaton Scenario
• Primordial non-Gaussianity from two curvaton decays
• Isocurvature, non-gaussianity and the curvaton model
• Non-Gaussianity and Baryonic Isocurvature Fluctuations in the Curvaton Scenario
• Non-Gaussianity from Baryon Asymmetry