Planck 2018 results

• Published in: Astronomy and astrophysics (Berlin) 2020-09, Vol.641
• Main Authors: Ashdown, M, Ballardini, M, Banday, A J, Barreiro, R B, Bartolo, N, Battye, R, J.-P. Bernard, Bersanelli, M, Bock, J J, Borrill, J, Bouchet, F R, Butler, R C, J.-F. Cardoso, Carron, J, Challinor, A, Chiang, H C, Chluba, J, Combet, C, de Bernardis, P, Delabrouille, J, E. Di Valentino, Diego, J M, Doré, O, Douspis, M, Ducout, A, Dusini, S, Elsner, F, Enßlin, T A, Fergusson, J, Finelli, F, astieri, F, Frailis, M, Frolov, A, Galeotta, S, Ganga, K, Gerbino, M, Ghosh, T, Górski, K M, Gratton, S, Gruppuso, A, Gudmundsson, J E, Hansen, F K, Huang, Z, Jaffe, A H, Karakci, A, Keihänen, E, Kiiveri, K, Kim, J, Knox, L, Krachmalnicoff, N, Kunz, M, J.-M. Lamarre, Lasenby, A, Lemos, P, Lesgourgues, J, Levrier, F, Lewis, A, Liguori, M, Lilje, P B, Lubin, P M, Y.-Z. Ma, Macías-Pérez, J F, Maggio, G, Maino, D, Mangilli, A, Maris, M, Martin, P G, Martínez-González, E, Migliaccio, M, Mitra, S, M.-A. Miville-Deschênes, Morgante, G, Nørgaard-Nielsen, H U, Paoletti, D, Patanchon, G, Perrotta, F, Pettorino, V, Piacentini, F, Polenta, G, J.-L. Puget, Rosset, C, Roudier, G, Rubiño-Martín, J A, Ruiz-Granados, B, Sandri, M, Savelainen, M, Sirignano, C, Sirri, G, Sunyaev, R, A.-S. Suur-Uski, Tauber, J A, Tenti, M, Tomasi, M, Trombetti, T, Valenziano, L, Valiviita, J, Vittorio, N, Wandelt, B D, White, S D M, Zonca, A
• Format: Article
• Language: English
• Subjects: Acoustic measurement; Amplitudes; Astronomical models; Baryons; Big bang cosmology; Clustering; Confidence; Constraint modelling; Cosmic microwave background; Cosmological constant; Cosmology; Dark matter; Density; Equations of state; Galaxies; Hubble constant; Ionization; Neutrinos; Nuclear fusion; Nuclei (nuclear physics); Optical thickness; Polarization; Reconstruction; Sky surveys (astronomy); Universe
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361/201833910

We present cosmological parameter results from the final full-mission Planck measurements of the cosmic microwave background (CMB) anisotropies, combining information from the temperature and polarization maps and the lensing reconstruction. Compared to the 2015 results, improved measurements of large-scale polarization allow the reionization optical depth to be measured with higher precision, leading to significant gains in the precision of other correlated parameters. Improved modelling of the small-scale polarization leads to more robust constraints on many parameters, with residual modelling uncertainties estimated to affect them only at the 0.5σ level. 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 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 (model-dependent) late-Universe parameters are: Hubble constant H0 = (67.4 ± 0.5)  km s−1 Mpc−1; 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 baryon acoustic oscillation (BAO) measurements (and considering single-parameter extensions) we constrain the effective extra relativistic degrees of freedom to be Neff = 2.99 ± 0.17, in agreement with the Standard Model prediction Neff = 3.046, and find that the neutrino mass is tightly constrained to ∑mν <  0.12  eV. 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 ΛCDM model; however, this is not supported by the lensing reconstruction or (in models that also change the background geometry) BAO data. The joint constraint with BAO measurements on spatial curvature is consistent with a flat