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

TL;DR

This paper applies the Correlated Component Analysis to WMAP 3-year data to investigate foreground emissions, revealing a persistent flat-spectrum synchrotron component, testing various models, and assessing their impact on the CMB power spectrum and anomalies.

Contribution

It introduces a comprehensive analysis of foreground components in WMAP data using CCA, testing multiple spectral models, and evaluating their effects on the CMB power spectrum and anomalies.

Findings

Detection of a widespread flat-spectrum synchrotron component.

Some foreground models are disfavored by quality tests.

The CMB power spectrum is consistent with WMAP, with some deviations.

Abstract

The Correlated Component Analysis (CCA) allows us to estimate how the different diffuse emissions mix in CMB experiments, exploiting also complementary information from other surveys. It is especially useful to deal with possible additional components. An application of CCA to WMAP maps assuming that only the canonical Galactic emissions 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(frequency) plane, and a grey body. 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 1 sigma below the expectation from the standard LambdaCDM 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. We also present a first, albeit preliminary, all-sky map of the "anomalous" component.