QUIJOTE scientific results - VIII. Diffuse polarized foregrounds from component separation with QUIJOTE-MFI

We derive linearly polarized astrophysical component maps in the Northern Sky from the QUIJOTE-MFI data at 11 and 13 GHz in combination with the Wilkinson Microwave Anisotropy Probe K and Ka bands (23 and 33 GHz) and all Planck polarized channels (30-353 GHz), using the parametric component separation method B-SeCRET. The addition of QUIJOTE-MFI data significantly improves the parameter estimation of the low-frequency foregrounds, especially the estimation of the synchrotron spectral index, beta(s). We present the first detailed beta(s) map of the Northern Celestial Hemisphere at a smoothing scale of 2 degrees. We find statistically significant spatial variability across the sky. We obtain an average value of -3.08 and a dispersion of 0.13, considering only pixels with reliable goodness of fit. The power-law model of the synchrotron emission provides a good fit to the data outside the Galactic plane but fails to track the complexity within this region. Moreover, when we assume a synchrotron model with uniform curvature, c(s), we find a value of c(s) = -0.0797 +/- 0.0012. However, there is insufficient statistical significance to determine which model is favoured, either the power law or the power law with uniform curvature. Furthermore, we estimate the thermal dust spectral parameters in polarization. Our cosmic microwave background, synchrotron, and thermal dust maps are highly correlated with the corresponding products of the PR4 Planck release, although some large-scale differences are observed in the synchrotron emission. Finally, we find that the beta(s) estimation in the high signal-to-noise synchrotron emission areas is prior-independent, while, outside these regions, the prior governs the beta(s) estimation.

Automated summary

We use a combination of data from various telescopes to obtain linearly polarized astrophysical component maps of the Northern Sky. The addition of QUIJOTE-MFI data improves the estimation of low-frequency foregrounds, particularly the synchrotron spectral index. We observe spatial variability in the beta(s) map and find that the power-law model of synchrotron emission fits well outside the Galactic plane but not within it. We also estimate thermal dust spectral parameters and find strong correlation with the Planck release.