Confirmation of the detection of B modes in the Planck polarization maps

One of the main problems of extracting the cosmic microwave background (CMB) from submm/mm observations is correcting for the galactic components, mainly synchrotron, free–free, and thermal dust emission, with the required accuracy. Through a series of papers, it has been demonstrated that this task can be fulfilled by means of simple neural networks with high confidence.

The main purpose of this paper is to demonstrate that the CMB BB power spectrum detected in the Planck 2015 polarization maps is present in the improved Planck 2017 maps with higher signal‐to‐noise ratio. Two features have been detected in the EB power spectrum in the new dataset, both with S/N ∼ 4.

The origin of these features is most likely leakage from E to B with a level of about 1%. This leakage does not significantly contribute to the detected BB power spectrum. The TB power spectrum is consistent with a zero signal. Altogether, the BB power spectrum is not consistent with the “canonical” tensor‐to‐scalar models combined with gravitational lensing spectra.

These results will provide additional strong arguments for support to the proposed polarization satellite projects to follow up on the Planck mission.