Primordial non-Gaussian signatures in CMB polarization

Abstract

We study the signatures of local type primordial non-Gaussianity, parametrized by fNL, of scalar perturbations in CMB polarization using the probability distribution functions, Minkowski Functionals and Betti numbers. We show that the lowest order non-Gaussian deviation of the PDF of the total polarization intensity is at order (fNLσ)2. We calculate the non-Gaussian deviations of Minkowski Functionals and Betti numbers from simulated polarization maps. If observational issues such as instrumental noise are ignored, we find that E mode polarization provides independent and equally strong constraint on fNL as temperature fluctuations. The constraint is expected to weaken when observational issues are included since the signal-to-noise ratio of polarization data is lower than that of temperature. The non-Gaussian signal in the total polarization intensity, however, is much weaker and has a relatively large cosmic variance and hence may not be useful for detecting local type non-Gaussianity.