Planck 2013 results. XVI. Cosmological parameters
Abstract
This paper presents the first cosmological results based on Planck measurements of the cosmic microwave background (CMB) temperature and lensingpotential power spectra. We find that the Planck spectra at high multipoles (ℓ ≳ 40) are extremely well described by the standard spatiallyflat sixparameter ΛCDM cosmology with a powerlaw spectrum of adiabatic scalar perturbations. Within the context of this cosmology, the Planck data determine the cosmological parameters to high precision: the angular size of the sound horizon at recombination, the physical densities of baryons and cold dark matter, and the scalar spectral index are estimated to be θ_{∗} = (1.04147 ± 0.00062) × 10^{2}, Ω_{b}h^{2} = 0.02205 ± 0.00028, Ω_{c}h^{2} = 0.1199 ± 0.0027, and n_{s} = 0.9603 ± 0.0073, respectively(note that in this abstract we quote 68% errors on measured parameters and 95% upper limits on other parameters). For this cosmology, we find a low value of the Hubble constant, H_{0} = (67.3 ± 1.2) km s^{1} Mpc^{1}, and a high value of the matter density parameter, Ω_{m} = 0.315 ± 0.017. These values are in tension with recent direct measurements of H_{0} and the magnituderedshift relation for Type Ia supernovae, but are in excellent agreement with geometrical constraints from baryon acoustic oscillation (BAO) surveys. Including curvature, we find that the Universe is consistent with spatial flatness to percent level precision using Planck CMB data alone. We use highresolution CMB data together with Planck to provide greater control on extragalactic foreground components in an investigation of extensions to the sixparameter ΛCDM model. We present selected results from a large grid of cosmological models, using a range of additional astrophysical data sets in addition to Planck and highresolution CMB data. None of these models are favoured over the standard sixparameter ΛCDM cosmology. The deviation of the scalar spectral index from unity isinsensitive to the addition of tensor modes and to changes in the matter content of the Universe. We find an upper limit of r_{0.002}< 0.11 on the tensortoscalar ratio. There is no evidence for additional neutrinolike relativistic particles beyond the three families of neutrinos in the standard model. Using BAO and CMB data, we find N_{eff} = 3.30 ± 0.27 for the effective number of relativistic degrees of freedom, and an upper limit of 0.23 eV for the sum of neutrino masses. Our results are in excellent agreement with big bang nucleosynthesis and the standard value of N_{eff} = 3.046. We find no evidence for dynamical dark energy; using BAO and CMB data, the dark energy equation of state parameter is constrained to be w = 1.13_{0.10}^{+0.13}. We also use the Planck data to set limits on a possible variation of the finestructure constant, dark matter annihilation and primordial magnetic fields. Despite the success of the sixparameter ΛCDM model in describing the Planck data at high multipoles, we note that this cosmology does not provide a good fit to the temperature power spectrum at low multipoles. The unusual shape of the spectrum in the multipole range 20 ≲ ℓ ≲ 40 was seen previously in the WMAP data and is a real feature of the primordial CMB anisotropies. The poor fit to the spectrum at low multipoles is not of decisive significance, but is an "anomaly" in an otherwise selfconsistent analysis of the Planck temperature data.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 November 2014
 DOI:
 10.1051/00046361/201321591
 arXiv:
 arXiv:1303.5076
 Bibcode:
 2014A&A...571A..16P
 Keywords:

 cosmic background radiation;
 cosmological parameters;
 early Universe;
 inflation;
 primordial nucleosynthesis;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 69 pages. Matches version to appear in Astronomy &