Impact of secondary non-Gaussianities on the search for primordial non-Gaussianity with CMB maps

When constraining the primordial non-Gaussianity parameter f(NL) with cosmic microwave background anisotropy maps, the bias resulting from the covariance between primordial non-Gaussianity and secondary non-Gaussianities to the estimator of f(NL) 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 f(NL) between 5 and 10. In the future, it will be necessary to jointly estimate the combined primordial and secondary contributions to the cosmic microwave background bispectrum and establish f(NL) by properly accounting for the confusion from secondary non-Gaussianities.