WMAP 3yr data with the CCA: anomalous emission and impact of component separation on the CMB power spectrum

The Correlated Component Analysis (CCA) allows us to estimate how the different diffuse emissions mix in CMB experiments, taking also into account complementary information from other surveys. It is especially useful to deal with possible additional components for which little or no prior information exists. An application of CCA to WMAP maps assuming that only the canonical Galactic emissions (synchrotron, free-free, and thermal dust) are present, highlights the widespread presence of a spectrally flat “synchrotron” component, largely uncorrelated with the synchrotron template, suggesting that an additional foreground is indeed required. We have tested various spectral shapes for such component, namely a power law as expected if it is flat synchrotron, and two spectral shapes that may fit the spinning dust emission: a parabola in the logS–log ν plane, and a grey body. If the spatial distribution of the additional (“anomalous”) component is not constrained a priori it is found to be always tightly correlated with thermal dust, but the correlation is not perfect. Quality tests applied to the reconstructed CMB maps clearly disfavour two of the models. The CMB power spectra, estimated from CMB maps reconstructed exploiting the three surviving foreground models, are generally consistent with the WMAP ones, although at least one of them gives a significantly higher quadrupole moment than found by the WMAP team. Taking foreground modeling uncertainties into account, we find that the mean quadrupole amplitude for the three “good” models is less than 1σ below the expectation from the standard ΛCDM model. Also the other reported deviations from model predictions are found not to be statistically significant, except for the excess power at l ≃ 40. We confirm the evidence for a marked north south asymmetry in the large scale (l < 20) CMB anisotropies, which is stable with respect to the foreground parametrization we adopted. We also present a first, albeit preliminary, all sky map of the “anomalous emission”.