Planck2018 results
Authors:   Planck Collaboration, Aghanim N. , Akrami Y. , Ashdown M. , Aumont J. , Baccigalupi C. , Ballardini M. , Banday A. J. , Barreiro R. B. , Bartolo N. , Basak S. , Benabed K. , Bernard J.-P. , Bersanelli M. , Bielewicz P. , Bock J. J. , Bond J. R. , Borrill J. , Bouchet F. R. , Boulanger F. , Bucher M. , Burigana C. , Butler R. C. , Calabrese E. , Cardoso J.-F. , Carron J. , Casaponsa B. , Challinor A. , Chiang H. C. , Colombo L. P. L. , Combet C. , Crill B. P. , Cuttaia F. , de Bernardis P. , de Rosa A. , de Zotti G. , Delabrouille J. , Delouis J.-M. , Di Valentino E. , Diego J. M. , Doré O. , Douspis M. , Ducout A. , Dupac X. , Dusini S. , Efstathiou G. , Elsner F. , Enßlin T. A. , Eriksen H. K. , Fantaye Y. , Fernandez-Cobos R. , Finelli F. , Frailis M. , Fraisse A. A. , Franceschi E. , Frolov A. , Galeotta S. , Galli S. , Ganga K. , Génova-Santos R. T. , Gerbino M. , Ghosh T. , Giraud-Héraud Y. , González-Nuevo J. , Górski K. M. , Gratton S. , Gruppuso A. , Gudmundsson J. E. , Hamann J. , Handley W. , Hansen F. K. , Herranz D. , Hivon E. , Huang Z. , Jaffe A. H. , Jones W. C. , Keihänen E. , Keskitalo R. , Kiiveri K. , Kim J. , Kisner T. S. , Krachmalnicoff N. , Kunz M. , Kurki-Suonio H. , Lagache G. , Lamarre J.-M. , Lasenby A. , Lattanzi M. , Lawrence C. R. , Le Jeune M. , Levrier F. , Lewis A. , Liguori M. , Lilje P. B. , Lilley M. , Lindholm V. , López-Caniego M. , Lubin P. M. , Ma Y.-Z. , Macías-Pérez J. F. , Maggio G. , Maino D. , Mandolesi N. , Mangilli A. , Marcos-Caballero A. , Maris M. , Martin P. G. , Martínez-González E. , Matarrese S. , Mauri N. , McEwen J. D. , Meinhold P. R. , Melchiorri A. , Mennella A. , Migliaccio M. , Millea M. , Miville-Deschênes M.-A. , Molinari D. , Moneti A. , Montier L. , Morgante G. , Moss A. , Natoli P. , Nørgaard-Nielsen H. U. , Pagano L. , Paoletti D. , Partridge B. , Patanchon G. , Peiris H. V. , Perrotta F. , Pettorino V. , Piacentini F. , Polenta G. , Puget J.-L. , Rachen J. P. , Reinecke M. , Remazeilles M. , Renzi A. , Rocha G. , Rosset C. , Roudier G. , Rubiño-Martín J. A. , Ruiz-Granados B. , Salvati L. , Sandri M. , Savelainen M. , Scott D. , Shellard E. P. S. , Sirignano C. , Sirri G. , Spencer L. D. , Sunyaev R. , Suur-Uski A.-S. , Tauber J. A. , Tavagnacco D. , Tenti M. , Toffolatti L. , Tomasi M. , Trombetti T. , Valiviita J. , Van Tent B. , Vielva P. , Villa F. , Vittorio N. , Wandelt B. D. , Wehus I. K. , Zacchei A. , Zonca A. 
Published: June 2020

We describe the legacyPlanckcosmic microwave background (CMB) likelihoods derived from the 2018 data release. The overall approach is similar in spirit to the one retained for the 2013 and 2015 data release, with a hybrid method using different approximations at low (ℓ <  30) and high (ℓ ≥ 30) multipoles, implementing several methodological and data-analysis refinements compared to previous releases. With more realistic simulations, and better correction and modelling of systematic effects, we can now make full use of the CMB polarization observed in the High Frequency Instrument (HFI) channels. The low-multipoleEEcross-spectra from the 100 GHz and 143 GHz data give a constraint on the ΛCDM reionization optical-depth parameterτto better than 15% (in combination with theTTlow-ℓdata and the high-ℓtemperature and polarization data), tightening constraints on all parameters with posterior distributions correlated withτ. We also update the weaker constraint onτfrom the joint TEB likelihood using the Low Frequency Instrument (LFI) channels, which was used in 2015 as part of our baseline analysis. At higher multipoles, the CMB temperature spectrum and likelihood are very similar to previous releases. A better model of the temperature-to-polarization leakage and corrections for the effective calibrations of the polarization channels (i.e., the polarization efficiencies) allow us to make full use of polarization spectra, improving the ΛCDM constraints on the parametersθMC,ωc,ωb, andH0by more than 30%, and nsby more than 20% compared to TT-only constraints. Extensive tests on the robustness of the modelling of the polarization data demonstrate good consistency, with some residual modelling uncertainties. At high multipoles, we are now limited mainly by the accuracy of the polarization efficiency modelling. Using our various tests, simulations, and comparison between different high-multipole likelihood implementations, we estimate the consistency of the results to be better than the 0.5 σlevel on the ΛCDM parameters, as well as classical single-parameter extensions for the joint likelihood (to be compared to the 0.3 σlevels we achieved in 2015 for the temperature data alone on ΛCDM only). Minor curiosities already present in the previous releases remain, such as the differences between the best-fit ΛCDM parameters for theℓ <  800 andℓ >  800 ranges of the power spectrum, or the preference for more smoothing of the power-spectrum peaks than predicted in ΛCDM fits. These are shown to be driven by the temperature power spectrum and are not significantly modified by the inclusion of the polarization data. Overall, the legacyPlanckCMB likelihoods provide a robust tool for constraining the cosmological model and represent a reference for future CMB observations.