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A comparison between Galactic magnetic field models and polarized synchrotron emission with C-BASS at 4.76 GHz and S-PASS at 2.3 GHz

Year: 2026
Type: preprint
Abstract: We compare a set of contemporary Galactic magnetic field (GMF) models with polarized synchrotron observations from the S-PASS and C-BASS radio surveys and combine them to create a reconstructed 4.76~GHz full sky map. Pixels that potentially have a large Faraday rotation are excluded while small ($< 80\degree$) Faraday corrections derived at the respective frequencies of the two surveys are applied to the rest of the map. Using a template-fitting approach, we evaluate the ability of each model to reproduce the observed polarization amplitudes and polarization angles. We find that while most GMF models match the polarization angles reasonably well, they often fail to reproduce the morphology of the polarized intensity. We find that for most models there is a clear correlation between the data and models in polarization angles on large scales, but this does not hold true for polarized intensity. Our results show that a large portion of the polarized sky is shaped by local ``foreground'' features such as the North Polar Spur/Loop\,I and the Fan region. We conclude that incorporating such local structures is essential for accurately modelling the polarized synchrotron emission at microwave frequencies.
Authors: Shaw, Vasundhara, Harper, S. E., Dickinson, C., Leahy, J. P., Hoerning, Gabriel A., Cepeda-Arroita, R., Weymann-Despres, Gilles, Peel, Mike, Taylor, Angela C., Pearson, T. J., Leech, Jamie, Jones, Michael
Institutions: FIZ Karlsruhe – Leibniz Institute for Information Infrastructure, University of Manchester, Instituto de Astrofísica de Canarias, University of Oxford, Imperial College London, California Institute of Technology
Open Access status: green
Funders: National Science Foundation, National Aeronautics and Space Administration, California Institute of Technology, UK Space Agency, UK Research and Innovation, University of Oxford, Rhodes University, Inyuvesi Yakwazulu-Natali, King Abdulaziz City for Science and Technology, HORIZON EUROPE Framework Programme, Science and Technology Facilities Council
Awards: G1492128961, The C-Band All Sky Survey: Separating the Polarization of the Cosmic Microwave Background from Galactic Foregrounds, A FOREGROUND AND CMB ANALYSIS COMBINING PLANCK, WMAP, AND C-BASS DATA. THIS PROJECT WILL COMBINE A NEW ALL-SKY 5-GHZ SURVEY, C-BASS, WITH THE WMAP AN, CBASS-South: Completing the C-Band All Sky Survey for the Southern Skies, The C-Band All Sky Survey: Diffuse Galactic Emission and CMB Polarization, Astrophysics and Cosmology Research within the JBCA 2017-2020, The C-Band All Sky Survey: Diffuse Galactic Emission and CMB Polarization, G7515359554, G831849349
OpenAlex ID: W7162474489
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