Binned Hubble parameter measurements and the cosmological deceleration-acceleration transition

TL;DR

This study combines multiple Hubble parameter measurements at different redshifts to analyze the universe's expansion history, confirming the transition from deceleration to acceleration around redshift 0.74 consistent with standard cosmological models.

Contribution

It introduces a method to bin and analyze H(z) data, demonstrating that combined lower and higher redshift measurements yield consistent cosmological constraints and support the deceleration-acceleration transition.

Findings

Transition redshift z_da = 0.74 ± 0.05

Binned data constraints match individual measurements

Results support dark energy dominated cosmology

Abstract

Weighted mean and median statistics techniques are used to combine 23 independent lower redshift, $z<1.04$, Hubble parameter, $H(z)$, measurements and determine binned forms of $H(z)$. When these are combined with 5 higher redshift, $1.3\leqslant z \leqslant 2.3$, $H(z)$ measurements the resulting constraints on cosmological parameters, of three cosmological models, that follow from the weighted-mean binned data are almost identical to those derived from analyses using the 28 independent $H(z)$ measurements. This is consistent with what is expected if the lower redshift measurements errors are Gaussian. Plots of the binned weighted-mean $H(z)/(1+z)$ versus $z$ data are consistent with the presence of a cosmological deceleration-acceleration transition at redshift $z_{\rm da}=0.74 \pm 0.05$ \citep{farooq3}, which is expected in cosmological models with present-epoch energy budget dominated by dark energy as in the standard spatially-flat $\Lambda$CDM cosmological model.