Hubble Parameter and Baryon Acoustic Oscillation Measurement Constraints on the Hubble Constant, the Deviation from the Spatially Flat ΛCDM Model, the Deceleration–Acceleration Transition Redshift, and Spatial Curvature

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We compile a complete collection of reliable Hubble parameter H ( z ) data to redshift z ≤ 2.36 and use them with the Gaussian Process method to determine continuous H ( z ) functions for various data subsets. From these continuous H ( z )'s, summarizing across the data subsets considered, we find H 0 ∼ 67 ± 4 km s −1 Mpc −1 , more consistent with the recent lower values determined using a variety of techniques. In most data subsets, we see a cosmological deceleration–acceleration transition at 2 σ significance, with the data subsets transition redshifts varying over at 1 σ significance. We find that the flat-ΛCDM model is consistent with the H ( z ) data to a z of 1.5 to 2.0, depending on data subset considered, with 2 σ deviations from flat-ΛCDM above this redshift range. Using the continuous H ( z ) with baryon acoustic oscillation distance-redshift observations, we constrain the current spatial curvature density parameter to be , consistent with a flat universe, but the large error bar does not rule out small values of spatial curvature that are now under debate.