COSMOGLOBE DR1 results II. Constraints on isotropic cosmic birefringence from reprocessed WMAP and Planck LFI data

Cosmic birefringence is a parity-violating effect that might have rotated the plane of linearly polarized light of the cosmic microwave background (CMB) by an angle beta since its emission. This has recently been measured to be non-zero at a statistical significance of 3.6 sigma in the official Planck PR4 and 9-year WMAP data. In this work, we constrain beta using the reprocessed BeyondPlanck LFI and Cosmoglobe DR1 WMAP polarization maps. These novel maps have both lower systematic residuals and a more complete error description than the corresponding official products. Foreground EB correlations could bias measurements of beta, and while thermal dust EB emission has been argued to be statistically non-zero, no evidence for synchrotron EB power has been reported. Unlike the dust-dominated Planck HFI maps, the majority of the LFI and WMAP polarization maps are instead dominated by synchrotron emission. Simultaneously constraining beta and the polarization miscalibration angle, alpha, of each channel, we find a best-fit value of beta=0.35(degrees)+/- 0.70(degrees) with LFI and WMAP data only. When including the Planck HFI PR4 maps, but fitting beta separately for dust-dominated, beta(>70GHz), and synchrotron-dominated channels, beta(<= 70GHz), we find beta(<= 70GHz)=0.53(degrees)+/- 0.28(degrees). This differs from zero with a statistical significance of 1.9 sigma, and the main contribution to this value comes from the LFI 70 GHz channel. While the statistical significances of these results are low on their own, the measurement derived from the LFI and WMAP synchrotron-dominated maps agrees with the previously reported HFI-dominated constraints, despite the very different astrophysical and instrumental systematics involved in all these experiments.