Combining full-shape and BAO analyses of galaxy power spectra: a 1.6% CMB-independent constraint onH₀

Abstract

We present cosmological constraints from a joint analysis of the pre- and post-reconstruction galaxy power spectrum multipoles from the final data release of the Baryon Oscillation Spectroscopic Survey (BOSS). Geometric constraints are obtained from the positions of BAO peaks in reconstructed spectra, which are analyzed in combination with the unreconstructed spectra in a full-shape (FS) likelihood using a joint covariance matrix, giving stronger parameter constraints than FS-only or BAO-only analyses. We introduce a new method for obtaining constraints from reconstructed spectra based on a correlated theoretical error, which is shown to be simple, robust, and applicable to any flavor of density-field reconstruction. Assuming ΛCDM with massive neutrinos, we analyze clustering data from two redshift bins zeff=0.38,0.61 and obtain 1.6% constraints on the Hubble constant H0, using only a single prior on the current baryon density ωb from Big Bang Nucleosynthesis (BBN) and no knowledge of the power spectrum slope ns. This gives H0 = 68.6±1.1 km s−1Mpc−1, with the inclusion of BAO data sharpening the measurement by 40%, representing one of the strongest current constraints on H0 independent of cosmic microwave background data, comparable with recent constraints using BAO data in combination with other data-sets. Restricting to the best-fit slope ns from Planck (but without additional priors on the spectral shape), we obtain a 1% H0 measurement of 67.8± 0.7 km s−1Mpc−1. Finally, we find strong constraints on the cosmological parameters from a joint analysis of the FS, BAO, and Planck data. This sets new bounds on the sum of neutrino masses ∑ mν < 0.14 eV (at 95% confidence) and the effective number of relativistic degrees of freedom Neff = 2.90+0.15−0.16, though contours are not appreciably narrowed by the inclusion of BAO data.

Nonlinear perturbation theory extension of the Boltzmann code CLASS

“…This likelihood was already used in Refs. [13][14][15], where one can find all technical details. We repeat it here just as an illustration.…”

“…In this section, for illustration purposes, we present the constraints obtained in this way for the base ΛCDM model. It is straightforward to repeat this analysis for more complicated beyond-ΛCDM models, see e.g., [25] for the analysis within wCDM and [14,15] for νΛCDM and νΛCDM þ N eff . We stress that the key novelty of our analysis is the most advanced theoretical model for the nonlinear power spectrum.…”

“…We believe that it is more appropriate to scan over this unknown parameter, as it is done in Refs. [13][14][15]. Our MCMC chains sample the remaining cosmological parameters of the minimal ΛCDM model: the physical density of dark matter ω cdm , the Hubble constant H 0 and the amplitude of primordial scalar fluctuations A s .…”

“…Besides, we publicly release a custom-built BOSS galaxy power spectrum likelihood written for the Markov Chain Monte Carlo sampler MONTEPYTHON [6,12], which can be used for various cosmological analyses. It is worth stressing that CLASS-PT has been already applied to the analysis of the BOSS data [13][14][15], and used in a blind cosmology challenge based on a large-volume numerical simulation [16]. Moreover, in Ref.…”

Constraining early dark energy with large-scale structure

“…Similarly, the combination of Dark Energy Survey (DES) [18] data and BOSS BAO data gives H 0 ¼ 67.4 þ1.1 −1.2 km=s=Mpc [19]. Measurements of the Hubble constant from galaxy clustering alone (without the Lyα data) can also be done using the full shape (FS) of the galaxy power spectrum [20][21][22][23]. In particular, the joint FS þ BAO data from BOSS yields H 0 ¼ 68.6 AE 1.1 km=s=Mpc [23], in excellent agreement with the CMB result.…”