B-mode constraints from Planck low-multipole polarization data. Issue 3 (15th November 2022)

• Record Type: Journal Article
• Authors: de Belsunce, Roger; Gratton, Steven; Efstathiou, George
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 518:Issue 3(2023)
• Page Start: 3675
• Page End: 3684
• Publication Date: 2022-11-15
• Subjects: methods: data analysis -- cosmic background radiation -- cosmological parameters; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac3321
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We present constraints on primordial B modes from large-angular scale cosmic microwave background polarization anisotropies measured with the Planck satellite. To remove Galactic polarized foregrounds, we use a Bayesian parametric component separation method, modelling synchrotron radiation as a power law and thermal dust emission as a modified blackbody. This method propagates uncertainties from the foreground cleaning into the noise covariance matrices of the maps. We construct two likelihoods: (i) a semi-analytical cross-spectrum-based likelihood-approximation scheme (momento ), and (ii) an exact polarization-only pixel-based likelihood (pixLike ). Since momento is based on cross-spectra, it is statistically less powerful than pixLike, but is less sensitive to systematic errors correlated across frequencies. Both likelihoods give a tensor-to-scalar ratio, r, that is consistent with zero from low-multipole (2 ≤ ℓ < 30) Planck polarization data. From full-mission maps, we obtain r 0.05 < 0.274 at 95 per cent confidence at a pivot scale of k * ≡ 0.05 Mpc −1, using pixLike . momento gives a qualitatively similar but weaker 95 per cent confidence limit of r 0.05 < 0.408.