In addition, the BAO data allow estimates of H 0 that are independent of the CMB data, with similar central values and precision under a Λ CDM model. The inverse distance ladder measurement under this model yields H 0 = 68.18 ± 0.79 km s − 1 Mpc − 1, remaining in tension with several direct determination methods the BAO data allow Hubble constant estimates that are robust against the assumption of the cosmological model. The dark energy constraints lead to w 0 = − 0.909 ± 0.081 and w a = − 0.4 9 − 0.30 + 0.35, corresponding to an equation of state of w p = − 1.018 ± 0.032 at a pivot redshift z p = 0.29 and a Dark Energy Task Force Figure of Merit of 94.
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In a model that allows for free curvature and a time-evolving equation of state for dark energy, the combined samples produce a constraint Ω k = − 0.0022 ± 0.0022.
Regardless of cosmological model, the precision on each of the three parameters, Ω Λ, H 0, and σ 8, remains at roughly 1%, showing changes of less than 0.6% in the central values between models. When combining the results of SDSS BAO and RSD, Planck, Pantheon Type Ia supernovae (SNe Ia), and DES weak lensing and clustering measurements, all multiple-parameter extensions remain consistent with a Λ CDM model. The combined BAO and RSD measurements indicate σ 8 = 0.85 ± 0.03, implying a growth rate that is consistent with predictions from Planck temperature and polarization data and with General Relativity. Independent of distance measurements, the SDSS RSD data complement weak lensing measurements from the Dark Energy Survey (DES) in demonstrating a preference for a flat Λ CDM cosmological model when combined with Planck measurements. When combined with Planck Cosmic Microwave Background (CMB) measurements of temperature and polarization, under the same model, the BAO data provide nearly an order of magnitude improvement on curvature constraints relative to primary CMB constraints alone. We show that the BAO data alone are able to rule out dark-energy-free models at more than eight standard deviations in an extension to the flat, Λ CDM model that allows for curvature. This composite sample is the most constraining of its kind and allows us to perform a comprehensive assessment of the cosmological model after two decades of dedicated spectroscopic observation. These experiments, composed of data from SDSS, SDSS-II, BOSS, and eBOSS, offer independent measurements of baryon acoustic oscillation (BAO) measurements of angular-diameter distances and Hubble distances relative to the sound horizon, r d, from eight different samples and six measurements of the growth rate parameter, f σ 8, from redshift-space distortions (RSD). We present the cosmological implications from final measurements of clustering using galaxies, quasars, and Ly α forests from the completed Sloan Digital Sky Survey (SDSS) lineage of experiments in large-scale structure.
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