Planck 2018 results. VI. Cosmological parameters

Change log
Collaboration, Planck 
Aghanim, N 
Akrami, Y 
Ashdown, M 
Aumont, J 

We present cosmological parameter results from the final full-mission Planck measurements of the CMB anisotropies. We find good consistency with the standard spatially-flat 6-parameter ΛCDM cosmology having a power-law spectrum of adiabatic scalar perturbations (denoted "base ΛCDM" in this paper), from polarization, temperature, and lensing, separately and in combination. A combined analysis gives dark matter density Ωch2=0.120±0.001, baryon density Ωbh2=0.0224±0.0001, scalar spectral index ns=0.965±0.004, and optical depth τ=0.054±0.007 (in this abstract we quote 68% confidence regions on measured parameters and 95% on upper limits). The angular acoustic scale is measured to 0.03% precision, with 100θ∗=1.0411±0.0003. These results are only weakly dependent on the cosmological model and remain stable, with somewhat increased errors, in many commonly considered extensions. Assuming the base-ΛCDM cosmology, the inferred late-Universe parameters are: Hubble constant H0=(67.4±0.5)km/s/Mpc; matter density parameter Ωm=0.315±0.007; and matter fluctuation amplitude σ8=0.811±0.006. We find no compelling evidence for extensions to the base-ΛCDM model. Combining with BAO we constrain the effective extra relativistic degrees of freedom to be Neff=2.99±0.17, and the neutrino mass is tightly constrained to mν<0.12eV. The CMB spectra continue to prefer higher lensing amplitudes than predicted in base -ΛCDM at over 2σ, which pulls some parameters that affect the lensing amplitude away from the base-ΛCDM model; however, this is not supported by the lensing reconstruction or (in models that also change the background geometry) BAO data. (Abridged)

cosmic background radiation, cosmological parameters
Journal Title
Astronomy and Astrophysics
Conference Name
Journal ISSN
Volume Title
EDP Sciences
Science and Technology Facilities Council (ST/L000636/1)
Science and Technology Facilities Council (ST/M007065/1)
Science and Technology Facilities Council (ST/P000673/1)
Science and Technology Facilities Council (ST/N000927/1)