Cosmology with the EFTofLSS and BOSS: dark energy constraints and a note on priors

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Abstract

We analyse the BOSS DR12 multipoles of the galaxy power spectrum jointly with measurements of the BAO scale for three different models of dark energy. We use recent measurements performed with a windowless estimator, and an independent and fast pipeline based on EFTofLSS modelling implemented via the FAST-PT algorithm to compute the integrals of the redshift-space loop corrections. We accelerate our analysis further by using the bacco linear power spectrum emulator instead of a Boltzmann solver. We perform two sets of analyses: one including 3 σ Planck priors on A _s and n _s , and another that is fully CMB-free, i.e., letting the primordial parameters vary freely. The first model we study is ΛCDM, within which we reproduce previous results obtained with the same estimator. We find a low value of the scalar amplitude in the CMB-free case, in agreement with many previous EFT-based full-shape analyses of the BOSS data. We then study wCDM, finding a lower value of the amplitude in the CMB-free run, coupled with a preference for phantom dark energy with w = -1.17 ^+0.12 _-0.11, again in broad agreement with previous results. Finally, we investigate the dark scattering model of interacting dark energy, which we label wACDM. In the CMB-free analysis, we find a large degeneracy between the interaction strength A and the amplitude A _s , hampering measurements of those parameters. On the contrary, in our run with a CMB prior, we are able to constrain the dark energy parameters to be w = -0.972 ^+0.036 _-0.029 and A = 3.9 ^+3.2 _-3.7, which show a 1 σ hint of interacting dark energy. This is the first measurement of this parameter and demonstrates the ability of this model to alleviate the σ ₈ tension. Our analysis can be used as a guide for the analysis of any model with scale-independent growth. Finally, we study the dependence of the results on the priors imposed on the nuisance parameters and find these priors to be informative, with their broadening generating shifts in the contours. We argue for an in depth study of this issue, which can affect current and forthcoming analyses of LSS data.

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emcee: The MCMC Hammer

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Planck 2018 results: VI. Cosmological parameters

N. Aghanim, Y. Akrami, M Ashdown … (2020)

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 0.5 σ 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 Ω c h 2 = 0.120 ± 0.001, baryon density Ω b h 2 = 0.0224 ± 0.0001, scalar spectral index n s = 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 100 θ * = 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 H 0 = (67.4 ± 0.5) km s −1 Mpc −1 ; matter density parameter Ω m = 0.315 ± 0.007; and matter fluctuation amplitude σ 8 = 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 N eff = 2.99 ± 0.17, in agreement with the Standard Model prediction N eff = 3.046, and find that the neutrino mass is tightly constrained to ∑ m ν < 0.12 eV. The CMB spectra continue to prefer higher lensing amplitudes than predicted in base ΛCDM at over 2 σ , 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, Ω K = 0.001 ± 0.002. Also combining with Type Ia supernovae (SNe), the dark-energy equation of state parameter is measured to be w 0 = −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 r 0.002 < 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, 3.6 σ , 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.