Planck2018 results

Abstract

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 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 (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 universe, ΩK = 0.001 ± 0.002. Also combining with Type Ia supernovae (SNe), the dark-energy equation of state parameter is measured to be w0 = −1.03 ± 0.03, consistent with a cosmological constant. We find no evidence for deviations from a purely power-law primordial spectrum, and combining with data from BAO, BICEP2, and Keck Array data, we place a limit on the tensor-to-scalar ratio r0.002 < 0.06. Standard big-bang nucleosynthesis predictions for the helium and deuterium abundances for the base-ΛCDM cosmology are in excellent agreement with observations. The Planck base-ΛCDM results are in good agreement with BAO, SNe, and some galaxy lensing observations, but in slight tension with the Dark Energy Survey’s combined-probe results including galaxy clustering (which prefers lower fluctuation amplitudes or matter density parameters), and in significant, 3.6σ, tension with local measurements of the Hubble constant (which prefer a higher value). Simple model extensions that can partially resolve these tensions are not favoured by the Planck data.

Kaluza-Klein FIMP dark matter in warped extra-dimensions

“…GeV, where ρ c 1.1×10 −5 h 2 GeV/cm 3 is the critical energy density, s 0 2.9×10 3 cm −3 is the entropy density at present and Ω χ h 2 0.12 [61]. The gray-shaded areas are the regions where…”

Revealing Reionization with the Thermal History of the Intergalactic Medium: New Constraints from the Lyα Flux Power Spectrum

“…In order to accurately bound the ULA power spectrum suppression scale, we marginalize over the slope n s ∈ [0.9, 0.995] and amplitude A s ∈ [1.2 × 10 −9 , 2.5 × 10 −9 ] of the primordial power spectrum, with a pivot scale k p = 2 Mpc −1 . Otherwise, we fix our cosmology to the baseline Planck 2018 parameters [49]: in particular, physical baryon energy density Ω b h 2 = 0.022126, physical dark matter energy density Ω c h 2 = 0.12068 and dimensionless Hubble parameter h = 0.6686.…”

“…Emulation and inference -In order to be able to sample the parameter space in a computationally-feasible manner, we "emulate" the flux power spectrum (at the discrete simulation sample wavenumbers) as a function of model parameters . We map from m a to [α, β, γ] using the parametric model defined above and fix Ω m = 0.3209 [49]. We follow the Bayesian emulator optimization method we presented in Refs.…”

“…Further, to prevent unphysical sudden changes in the IGM [e. g., 28,29] in adjacent redshift bins (which would be inconsistent with previous observations [e. g., 60]), we prevent changes in T 0 greater than 5000 K and changes in u 0 greater than 10 eV m −1 p (m p being the proton mass). We use Planck 2018-motivated [49] priors on n s and A s (translated to the pivot scale we use): Gaussian distributions respectively with means 0.9635 and 1.8296 × 10 −9 and respectively standard deviations 0.0057 and 0.030 × 10 −9 . In order to disfavor very cold IGMs which are hard to motivate physically [e. g., 36] and following previous analyses [e. g., 29, 31, 61], we use a conservative Gaussian prior on T 0 (z = z i ) with means set to our fiducial model ([8022, 7651, 8673] K at z = [5.0, 4.6, 4.2]) and standard deviations of 3000 K. As the effective optical depth is otherwise poorly constrained by our data and following Ref.…”

Shining light on the scotogenic model: interplay of colliders and cosmology

“…Current measurements by the Planck collaboration allow for an upper limit of ∆N eff ≈ 0.28 at 95% CL (TT, TE, EE+lowE+lensing+BAO). Including the present tension in the Hubble constant measurement, this value increases to ∆N eff ≈ 0.52 at 95 % CL (TT, TE, EE+lowE+lensing+BAO+R18) [53]. In the following, we dub the first value aggressive and the second one conservative.…”