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

TL;DR

This paper confirms the detection of B-modes in the Planck polarization maps, demonstrating their presence with higher confidence in improved data, and discusses implications for future polarization satellite missions.

Contribution

It provides evidence of B-modes in the 2017 Planck polarization maps with higher signal-to-noise ratio, supporting future satellite polarization studies.

Findings

Detection of B-mode polarization with higher confidence in 2017 data

Identification of features in the EB power spectrum likely due to leakage

BB power spectrum inconsistent with canonical models

Abstract

One of the main problems for extracting the Cosmic Microwave Background (CMB) from submm/mm observations is to correct 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 data set, both with S/N $\sim$4 . The origin of these features is most likely leakage from E to B with a level of about 1 per cent. This leakage gives no significant contribution 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 give additional strong arguments for support to the proposed polarization satellite projects to follow up on the Planck mission .