Cosmological implications of baryon acoustic oscillation measurements

Abstract

We derive constraints on cosmological parameters and tests of dark energy models from the combination of baryon acoustic oscillation (BAO) measurements with cosmic microwave background (CMB) data and a recent reanalysis of Type Ia supernova (SN) data. In particular, we take advantage of high-precision BAO measurements from galaxy clustering and the Lyman-α forest (LyaF) in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). Treating the BAO scale as an uncalibrated standard ruler, BAO data alone yield a high confidence detection of dark energy; in combination with the CMB angular acoustic scale they further imply a nearly flat universe. Adding the CMB-calibrated physical scale of the sound horizon, the combination of BAO and SN data into an "inverse distance ladder" yields a measurement of H0 = 67.3 ± 1.1 km s −1 Mpc −1 , with 1.7% precision. This measurement assumes standard pre-recombination physics but is insensitive to assumptions about dark energy or space curvature, so agreement with CMB-based estimates that assume a flat ΛCDM cosmology is an important corroboration of this minimal cosmological model. For constant dark energy (Λ), our BAO+SN+CMB combination yields matter density Ωm = 0.301 ± 0.008 and curvature Ω k = −0.003 ± 0.003. When we allow more general forms of evolving dark energy, the BAO+SN+CMB parameter constraints are always consistent with flat ΛCDM values at ≈ 1σ. While the overall χ 2 of model fits is satisfactory, the LyaF BAO measurements are in moderate (2 − 2.5σ) tension with model predictions. Models with early dark energy that tracks the dominant energy component at high redshift remain consistent with our expansion history constraints, and they yield a higher H0 and lower matter clustering amplitude, improving agreement with some low redshift observations. Expansion history alone yields an upper limit on the summed mass of neutrino species, mν < 0.56 eV (95% confidence), improving to mν < 0.25 eV if we include the lensing signal in the Planck CMB power spectrum. In a flat ΛCDM model that allows extra relativistic species, our data combination yields N eff = 3.43 ± 0.26; while the LyaF BAO data prefer higher N eff when excluding galaxy BAO, the galaxy BAO alone favor N eff ≈ 3. When structure growth is extrapolated forward from the CMB to low redshift, standard dark energy models constrained by our data predict a level of matter clustering that is high compared to most, but not all, observational estimates.

Constraining the cosmic deceleration-acceleration transition with type Ia supernova, BAO/CMB and H(z) data

“…In the bottom panels we also show the results for the SN Ia + BAO/CMB(Planck) + H(z) data, but marginalized over H 0 with Gaussian priors. In the bottom left panel we used as prior for H 0 , the Riess et al [41] measurement (red lines) and in the bottom right we used the Aubourg et al [42] result (green lines). Now the constraints are tighter, making clear the important role of the H 0 prior when including H(z) data.…”

On the concordance of cosmological data in the case of the generalized Chaplygin gas

“…The drag redshift z drag can be determined by using fitting formulae [43,44] but since we are dealing with cosmological models that possibly leave the validity domain of the parameter space where these fitting formulae are valid, we use the exact approach. A drag depth is defined as [45] …”

“…In addition, the BAO data obtained from the quasar-Lyman α cross-correlation of the Data Release 11 of the SDSS-III/BOSS [50] are taken into account. Although both Lyman α data sets are derived from the same volume, they can be considered as independent data points as stated in [44]. The auto-correlation and cross-correlation approaches are complementary because of the quite different impact of redshift-space distortion on the two measurements.…”

“…The auto-correlation and cross-correlation approaches are complementary because of the quite different impact of redshift-space distortion on the two measurements. These BAO data can be considered as independent because their uncertainties are not dominated by cosmic variance, but instead are dominated by the combination of noise in the spectra and sparse sampling of the structure in the survey volume, both of which affect the auto-correlation and cross-correlation almost independently [44]. In order to substantiate this, tests with mock catalogues and several analysis procedures are carried out in [49], which find a good agreement between error estimates from the likelihood function and from the variance in mock catalogues.…”

Mock Quasar-Lyman-α forest data-sets for the SDSS-III Baryon Oscillation Spectroscopic Survey

“…Measuring large-scale structure with these tracers provides percent-level accuracy in the position of the BAO peak [3], which translates into measurements of the redshift dependent angular diameter distance, D A (z), and Hubble expansion rate, H(z).…”