CMB constraint on non-Gaussianity in isocurvature perturbations

Journal Article · Mon Jul 01 04:00:00 EDT 2013 · Journal of Cosmology and Astroparticle Physics

DOI:https://doi.org/10.1088/1475-7516/2013/07/007· OSTI ID:22282802

Hikage, Chiaki ^[1]; Kawasaki, Masahiro ^[2]; Sekiguchi, Toyokazu ^[3]; Takahashi, Tomo ^[4]

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1. Kobayashi-Maskawa Institute, Nagoya University, Nagoya 464-8602 (Japan)
2. Institute for Cosmic Ray Research, University of Tokyo, Kashiwa 277-8582 (Japan)
3. Department of Physics and Astrophysics, Nagoya University, Nagoya 464-8602 (Japan)
4. Department of Physics, Saga University, Saga 840-8502 (Japan)

We study the CMB constraints on non-Gaussianity in CDM isocurvature perturbations. Non-Gaussian isocurvature perturbations can be produced in various models at the very early stage of the Universe. Since the isocurvature perturbations little affect the structure formation at late times, CMB is the best probe of isocurvature non-Gaussianity at least in the near future. In this paper, we focus on non-Gaussian curvature and isocurvature perturbations of the local-type, which are uncorrelated and in the form ζ = ζ{sub G}+(3/5)f{sub NL}(ζ{sub G}{sup 2}−(ζ{sub G}{sup 2})) and S = S{sub G}+f{sub NL}{sup (ISO)}(S{sub G}−(S{sub G}{sup 2})), and constrain the non-linearity parameter of isocurvature perturbations, f{sub NL}{sup (ISO)}, as well as the curvature one f{sub NL}. For this purpose, we employ several state-of-art techniques for the analysis of CMB data and simulation. Assuming that isocurvature perturbations are subdominant, we apply our method to the WMAP 7-year data of temperature anisotropy and obtain constraints on a combination α{sup 2}f{sub NL}{sup (ISO)}, where α is the ratio of the power spectrum of isocurvature perturbations to that of the adiabatic ones. When the adiabatic perturbations are assumed to be Gaussian, we obtained a constraint α{sup 2}f{sub NL}{sup (ISO)} = 40±66 assuming the power spectrum of isocurvature perturbations is scale-invariant. When we assume that the adiabatic perturbations can also be non-Gaussian, we obtain f{sub NL} = 38±24 and α{sup 2}f{sub NL}{sup (ISO)} = −8±72. We also discuss implications of our results for the axion CDM isocurvature model.

• OSTI ID: 22282802
• Journal Information: Journal of Cosmology and Astroparticle Physics, Journal Name: Journal of Cosmology and Astroparticle Physics Journal Issue: 07 Vol. 2013; ISSN 1475-7516
• Country of Publication: United States
• Language: English

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