Cosmological parameters derived from the final (PR4) Planck data release

TL;DR

This Planck PR4 analysis introduces an upgraded high-$\ell$ CMB likelihood (HiLLiPoP V4.2) and a low-$\ell$ polarization likelihood (LoLLiPoP) to extract cosmological parameters from the final Planck data. Foregrounds are modelled physically in the spectra domain, enabling robust $\Lambda$CDM constraints with 10–20% smaller uncertainties and allowing single-parameter extensions such as $A_L$, $Ω_K$, $N_{ ext{eff}}$, and $\sum m_ν$. Key results include $A_L = 1.039 \pm 0.052$, $Ω_K = -0.012 \pm 0.010$, $N_{ ext{eff}} = 3.08 \pm 0.17$, and $\sum m_ν < 0.39$ eV (95% CL) for TTTEEE, with lensing and BAO data further tightening these bounds and favoring a flat geometry. Overall, Planck PR4 provides the most constraining Planck-only cosmological constraints to date, showing improved consistency with $\Lambda$CDM and reducing tensions with large-scale structure measurements, while demonstrating the robustness of foreground modelling in the cross-spectrum framework.

Abstract

We present constraints on cosmological parameters using maps from the last Planck data release (PR4). In particular, we detail an upgraded version of the cosmic microwave background likelihood, HiLLiPoP, based on angular power spectra and relying on a physical modelling of the foreground residuals in the spectral domain. This new version of the likelihood retains a larger sky fraction (up to 75%) and uses an extended multipole range. Using this likelihood, along with low-l measurements from LoLLiPoP, we derive constraints on $Λ$CDM parameters that are in good agreement with previous Planck 2018 results, but with 10% to 20% smaller uncertainties. We demonstrate that the foregrounds can be accurately described in spectra domain with only negligible impact on $Λ$CDM parameters. We also derive constraints on single-parameter extensions to $Λ$CDM including $A_L$, $Ω_K$, $N_{eff}$, and $\sum m_ν$. Noteworthy results from this updated analysis include a lensing amplitude value of $A_L = 1.039 \pm 0.052$, which aligns more closely with theoretical expectations within the $Λ$CDM framework. Additionally, our curvature measurement, $Ω_K = -0.012 \pm 0.010$, now demonstrates complete consistency with a flat universe, and our measurement of $S_8$ is closer to the measurements derived from large-scale structure surveys (at the 1.6$σ$ level). We also add constraints from PR4 lensing, making the combination the most constraining data set that is currently available from Planck. Additionally we explore adding baryon acoustic oscillation data, which tightens limits on some particular extensions to the standard cosmology.