We study a possibility of constraining isotropic cosmic birefringence with help of cosmic microwave background polarization data in the presence of polarization angle miscalibration without relying on any assumptions about the Galactic foreground angular power spectra and in particular, on the correlation between their E- and B-modes. For this purpose, we propose a new analysis framework based on a generalized parametric component separation approach, which accounts simultaneously on the presence of Galactic foregrounds, relevant instrumental effects, and external priors. We find that upcoming multifrequency cosmic microwave background (CMB) data with appropriate calibration priors will allow producing an instrumental-effect-corrected and foreground-cleaned CMB map, which can be used to estimate the isotropic birefringence angle and the tensor-to-scalar ratio, accounting on statistical and systematic uncertainties incurred during the entire procedure. In particular, in the case of a Simons Observatory-like, three small aperture telescopes, we derive an uncertainty on the birefringence angle of $\sigma ({\beta }_b)=0.07°$ (0.1°), assuming the standard cosmology and calibration priors for all (one) frequency channels with the precision of $\sigma ({\alpha }_i)=0.1°$ as aimed at by the near future ground-based multifrequency experiments. This implies that these experiments could confirm or disprove the recently detected value of ${\beta }_b=0.35°$ with a significance between 3 and $5\sigma$. We furthermore explore the impact of precision of the calibration priors and of foreground complexity on our results and discuss requirements on the calibration precision. In addition, we also investigate constraints on the tensor-to-scalar ratio, $r$, which can be derived in the presence of isotropic birefringence and/or polarization angle miscalibration. We find that the proposed method allows setting constraints on $r$ in such cases, even if no prior is available, and with only a minor increase of the final uncertainty as compared to cases without these effects.

• Received 3 April 2023
• Accepted 12 September 2023

DOI:https://doi.org/10.1103/PhysRevD.108.082005