Cosmoglobe DR1. III. First full-sky model of polarized synchrotron emission from all WMAP and Planck LFI data

We present the first model of full-sky polarized synchrotron emission that is derived from all WMAP and Planck LFI frequency maps. The basis of this analysis is the set of end-to-end reprocessed Cosmoglobe Data Release 1 sky maps presented in a companion paper, which have significantly lower instrumental systematics than the legacy products from each experiment. We find that the resulting polarized synchrotron amplitude map has an average noise rms of 3.2 μK at 30 GHz and 2◦ FWHM, 30 % lower than the recently released BeyondPlanck model that included only LFI+WMAP Ka–V data, and 29 % lower than the raw WMAP K-band sensitivity. The mean EE/BB power spectrum ratio is 0.46 ± 0.03, with amplitudes consistent with those measured previously by Planck and QUIJOTE. Assuming a power law model for the synchrotron spectral energy distribution, we find a full-sky inverse noise-variance weighted mean of βs = −3.07±0.03 between WMAP K-band and LFI 30 GHz, in good agreement with previous estimates. In summary, the novel Cosmoglobe DR1 synchrotron model is both more sensitive and systematically cleaner than similar previous models, and it has a more complete error description that is defined by a set of Monte Carlo posterior samples. We believe that these products are preferable for all synchrotron-related scientific applications compared to the official maps, including simulation, forecasting and component separation