Searching for the non-gaussian signature of the CMB secondary anisotropies

In a first paper (Forni & Aghanim 1999), we developed several statistical discriminators to test the non-gaussian nature of a signal. These tests are based on the study of the coefficients in a wavelet decomposition basis. In this paper, we apply them in a cosmological context, to the study of the nature of the Cosmic Microwave Background (CMB) anisotropies. The latter represent the superposition of primary anisotropy imprints of the initial density perturbations and secondary ones due to photon interactions after recombination. In an inflationary scenario (standard Cold Dark Matter) with gaussian distributed fluctuations, we study the statistical signature of the secondary effects. More specifically, we investigate the dominant effects arising from the Compton scattering of CMB photons in ionised regions of the Universe: the Sunyaev-Zel'dovich effect of galaxy clusters and the effects of a spatially inhomogeneous re-ionisation of the Universe. Our study specifies and predicts the non-gaussian signature of the secondary anisotropies induced by these scattering effects. We find that our statistical discriminators allow us to distinguish and highlight the non-gaussian signature of a process even if it is combined with a larger gaussian one. We investigate the detectability of the secondary anisotropy non-gaussian signature in the context of the future CMB satellites (MAP and Planck Surveyor).