Cosmological implications of baryon acoustic oscillation (BAO) measurements

AUBOURG, ÉRIC ET AL (BOSS COLLABORATION); SCOCCOLA, CLAUDIA GRACIELA

PHYSICAL REVIEW D

AMER PHYSICAL SOC

Lugar: New York; Año: 2015 vol. 92 p. 1 - 38

1550-7998

We derive constraints on cosmological parameters and tests of darkenergy models from the combination of baryon acoustic oscillation (BAO)measurements with cosmic microwave background (CMB) data and a recentreanalysis of Type Ia supernova (SN) data. In particular, we takeadvantage of high-precision BAO measurements from galaxy clustering andthe Lyman-α forest (LyaF) in the SDSS-III Baryon OscillationSpectroscopic Survey (BOSS). Treating the BAO scale as an uncalibratedstandard ruler, BAO data alone yield a high confidence detection of darkenergy; in combination with the CMB angular acoustic scale they furtherimply a nearly flat universe. Adding the CMB-calibrated physical scaleof 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 prerecombination physics but isinsensitive to assumptions about dark energy or space curvature, soagreement with CMB-based estimates that assume a flat Λ CDMcosmology is an important corroboration of this minimal cosmologicalmodel. For constant dark energy (Λ ), our BAO +SN +CMBcombination yields matter density Ωm=0.301±0.008 and curvature Ωk=-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 Λ CDMvalues at ≈1 σ . While the overall χ2 of modelfits is satisfactory, the LyaF BAO measurements are in moderate (2 - 2.5σ ) tension with model predictions. Models with early dark energythat tracks the dominant energy component at high redshift remainconsistent with our expansion history constraints, and they yield ahigher H0 and lower matter clustering amplitude, improvingagreement with some low redshift observations. Expansion history aloneyields 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 thePlanck CMB power spectrum. In a flat Λ CDM model that allowsextra relativistic species, our data combination yieldsNeff=3.43 ±0.26 ; while the LyaF BAO data preferhigher Neff when excluding galaxy BAO, the galaxy BAO alonefavor Neff≈3 . When structure growth is extrapolatedforward from the CMB to low redshift, standard dark energy modelsconstrained by our data predict a level of matter clustering that ishigh compared to most, but not all, observational estimates.