Impact of Secondary non-Gaussianities on the Search for Primordial Non-Gaussianity with CMB Maps
Abstract
When constraining the primordial non-Gaussianity parameter fNL with cosmic microwave background anisotropy maps, the bias resulting from the covariance between primordial non-Gaussianity and secondary non-Gaussianities to the estimator of fNL is generally assumed to be negligible. We show that this assumption may not hold when attempting to measure the primordial non-Gaussianity out to angular scales below a few tens arcminutes with an experiment like Planck, especially if the primordial non-Gaussianity parameter is around the minimum detectability level with fNL between 5 and 10. In future, it will be necessary to jointly estimate the combined primordial and secondary contributions to the CMB bispectrum and establish fNL by properly accounting for the confusion from secondary non-Gaussianities.