Limits on Second-Order Non-Gaussianity from Minkowski Functionals of WMAP Data

TL;DR

This paper uses Minkowski functionals to analyze WMAP 7-year data, setting limits on primordial non-Gaussianity parameters without detecting any significant non-Gaussian signals.

Contribution

It applies second-order perturbative Minkowski functional formulae to constrain various types of primordial non-Gaussianity in CMB data, extending previous analyses.

Findings

No significant primordial non-Gaussianity detected.

Constraints on f_NL, tau_NL, and g_NL parameters are provided.

Results are consistent with previous skewness and kurtosis limits.

Abstract

We analyze non-Gaussianity (NG) due to the primordial bispectrum and trispectrum using CMB temperature maps of WMAP 7-year data. We first apply the perturbative formulae of Minkowski functionals up to second-order NG derived by Matsubara (2010), which enable us to give limits on cubic NG parametrized with tau_NL and g_NL as well as various types of quadratic NG parametrized with f_NL. We find no signature of primordial NG in WMAP 7-year data, but give constraints on the local-type, equilateral-type, orthogonal-type f_NL: f_NL(loc)=20+-42, f_NL(eq)=-121+-208, f_NL(ort)=-129+-171, respectively, and tau_NL/10^4=-7.6+-8.7, and g_NL/10^5=-1.9+-6.4. We also find that these constraints are consistent with the limits from skewness and kurtosis parameters which characterize the perturbative corrections of MFs.