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

**Authors:** D. J. Watts, U. Fuskeland, R. Aurlien, A. Basyrov, L. A. Bianchi, M. Brilenkov, H. K. Eriksen, K. S. F. Fornazier, M. Galloway, E. Gjerløw, B. Hensley, L. T. Hergt, D. Herman, H. Ihle, K. Lee, J. G. S. Lunde, S. K. Nerval, M. San, N. O. Stutzer, H. Thommesen  
**arXiv:** [2310.13740](https://arxiv.org/abs/2310.13740)  
**Date:** 2023-10-20  
**Summary page:** https://www.summarizepaper.com/en/arxiv-id/2310.13740v1/

## Key points

- Researchers present a model of full-sky polarized synchrotron emission using WMAP and Planck LFI frequency maps
- Utilize end-to-end reprocessed Cosmoglobe Data Release 1 sky maps with lower instrumental systematics
- Resulting polarized synchrotron amplitude map has lower noise rms compared to previous models
- Estimation of the B-to-E power spectrum ratio consistent with measurements by previous experiments
- Full-sky inverse noise-variance weighted mean between Cosmoglobe DR1 K-band and 30 GHz is in agreement with previous estimates
- Cosmoglobe DR1 synchrotron model provides improved sensitivity and cleaner results compared to previous models
- Offers more comprehensive error description based on Monte Carlo posterior samples
- Preferred for various synchrotron-related scientific applications, including simulation, forecasting, and component separation
- Estimating βs is challenging due to dependence on differences between frequencies, timestreams analysis improves estimation
- Joint analyses with experiments like QUIJOTE and CLASS expected to enhance understanding of the polarized sky
- Data products used include WMAP and Planck LFI maps focusing on frequencies suitable for tracing synchrotron emission while disregarding thermal dust and CMB emission contributions

## Summary

In this study, the researchers present a model of full-sky polarized synchrotron emission derived from all WMAP and Planck LFI frequency maps. They utilize the end-to-end reprocessed Cosmoglobe Data Release 1 sky maps, which have significantly lower instrumental systematics compared to previous products. The resulting polarized synchrotron amplitude map exhibits an average noise rms of $3.2\,\mathrm{\mu K}$ at 30 GHz and $2^{\circ}$ FWHM, which is 30% lower than the recently released BeyondPlanck model that only included LFI+WMAP Ka-V data, and 29% lower than the WMAP K-band map alone. The analysis also includes the estimation of the $B$-to-$E$ power spectrum ratio, which is found to be $0.40\pm0.02$, consistent with measurements by previous experiments such as Planck and QUIJOTE. By assuming a power law model for the synchrotron spectral energy distribution and using the $T$--$T$ plot method, the researchers find a full-sky inverse noise-variance weighted mean of $\beta_{\mathrm{s}}=-3.07\pm0.07$ between Cosmoglobe DR1 K-band and 30 GHz, in agreement with previous estimates. The authors highlight that their Cosmoglobe DR1 synchrotron model provides improved sensitivity and cleaner results compared to previous models. It also offers a more comprehensive error description based on Monte Carlo posterior samples. These products are considered preferable for various synchrotron-related scientific applications, including simulation, forecasting, and component separation. The paper emphasizes that estimating $\beta_{\mathrm{s}}$ is challenging due to its dependence on differences between different frequencies, which can amplify systematic effects and processing choices. The use of timestreams rather than purely map-based analysis enables the improvement demonstrated in this study. Furthermore, joint analyses incorporating data from experiments with complementary observation strategies, such as QUIJOTE and CLASS, are expected to further enhance our understanding of the polarized sky. The data products used in this research include the WMAP and Planck LFI maps focusing on frequencies ranging from 23 to 33 GHz; these frequencies are suitable for tracing synchrotron emission while disregarding thermal dust and CMB emission contributions. The legacy products from WMAP provide maps at various frequencies with varying angular resolutions; meanwhile Planck LFI offers lower white noise levels but higher angular resolutions compared to WMAP's offerings overall making them valuable information sources for this study's purpose . This study presents a comprehensive model of polarized synchrotron emission based on all available WMAP and Planck LFI frequency maps; its improved sensitivity reduces systematic effects while providing thorough error descriptions through Monte Carlo posterior samples making it a valuable tool for scientific applications related to synchrotron emission studies . Future joint analyses involving additional experiments will contribute further towards our knowledge about polarized skies .