Improved Constraints on Cosmic Birefringence from the WMAP and Planck Cosmic Microwave Background Polarization Data

TL;DR

This paper presents new measurements of cosmic birefringence using combined Planck and WMAP polarization data, detecting a small rotation angle of the polarization plane with high statistical significance, and finds no frequency dependence.

Contribution

The study provides the most precise measurement to date of cosmic birefringence by jointly analyzing Planck and WMAP data, improving constraints on parity-violating physics in the universe.

Findings

Measured birefringence angle β = 0.342° with 68% confidence

Excluded zero birefringence at 99.987% confidence level

No evidence found for frequency dependence of β

Abstract

The observed pattern of linear polarization of the cosmic microwave background (CMB) photons is a sensitive probe of physics violating parity symmetry under inversion of spatial coordinates. A new parity-violating interaction might have rotated the plane of linear polarization by an angle $\beta$ as the CMB photons have been traveling for more than 13 billion years. This effect is known as "cosmic birefringence." In this paper, we present new measurements of cosmic birefringence from a joint analysis of polarization data from two space missions, Planck and WMAP. This dataset covers a wide range of frequencies from 23 to 353 GHz. We measure $\beta = 0.342^{\circ\,+0.094^\circ}_{\phantom{\circ\,}-0.091^\circ}$ (68% C.L.) for nearly full-sky data, which excludes $\beta=0$ at 99.987% C.L. This corresponds to the statistical significance of $3.6\sigma$. There is no evidence for frequency dependence of $\beta$. We find a similar result, albeit with a larger uncertainty, when removing the Galactic plane from the analysis.