| Non-Gaussianities from Perturbing Recombination (2008) | |||||||||
Abstract | |||||||||
| We approximately compute the bispectrum induced on the CMB by fluctuations in the standard recombination history. Of all the second order sources that can induce non-Gaussianity during recombination, we concentrate on those proportional to the perturbation in the free electron density, which is about a factor of 5 larger than the other first order perturbations. This term induces some non-Gaussianity by delaying the time of recombination, by changing the shape of the visibility function, and by changing the photon diffusion scale. We find that the signal is not scale invariant, peaked on squeezed triangles with the smaller multipole around the scale of the first acoustic peak, and that its size corresponds to an effective f_NL~=-5, which could be detected by Planck.. Comment: 37 pages, 13 figures | |||||||||
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