Utility of observational Hubble parameter data on dark energy evolution

TL;DR

This study uses observational Hubble parameter data to test the Lambda Cold Dark Matter model and estimate the Hubble constant, revealing some deviations but generally supporting the model's validity within confidence levels.

Contribution

It introduces a model-independent test of dark energy evolution using OHD and compares results with Planck constraints, providing new estimates of Hubble constant from observational data.

Findings

Two pairs of OHD are consistent with LambdaCDM at 1σ

Two pairs are compatible at 2σ, while two are not compatible even at 2σ

Estimated Hubble constant values are 71.23±1.54 and 69.37±1.59 km/s/Mpc

Abstract

Aiming at exploring the nature of dark energy, we use thirty-six observational Hubble parameter data (OHD) in the redshift range $0 \leqslant z \leqslant 2.36$ to make a cosmological model-independent test of the two-point $Omh^2(z_{2};z_{1})$ diagnostic. In $\Lambda$CDM, we have $Omh^2 \equiv \Omega_{m}h^2$, where $\Omega_{m}$ is the matter density parameter at present. We bin all the OHD into four data points to mitigate the observational contaminations. By comparing with the value of $\Omega_{m}h^2$ which is constrained tightly by the Planck observations, our results show that in all six testing pairs of $Omh^2$ there are two testing pairs are consistent with $\Lambda$CDM at $1\sigma$ confidence level (CL), whereas for another two of them $\Lambda$CDM can only be accommodated at $2\sigma$ CL. Particularly, for remaining two pairs, $\Lambda$CDM is not compatible even at $2\sigma$ CL. Therefore it is reasonable that although deviations from $\Lambda$CDM exist for some pairs, cautiously, we cannot rule out the validity of $\Lambda$CDM. We further apply two methods to derive the value of Hubble constant $H_0$ utilizing the two-point $Omh^2(z_{2};z_{1})$ diagnostic. We obtain $H_0 = 71.23\pm1.54$ ${\mathrm{km \ s^{-1} \ Mpc^{-1}}}$ from inverse variance weighted $Omh^2$ value (method (I)) and $H_0 = 69.37\pm1.59$ ${\mathrm{km \ s^{-1} \ Mpc^{-1}}}$ that the $Omh^2$ value originates from Planck measurement (method (II)), both at $1\sigma$ CL. Finally, we explore how the error in OHD propagate into $w(z)$ at certain redshift during the reconstruction of $w(z)$. We argue that the current precision on OHD is not sufficient small to ensure the reconstruction of $w(z)$ in an acceptable error range, especially at the low redshift