Measurements of H_0 and reconstruction of the dark energy properties from a model-independent joint analysis

Alexander Bonilla,Suresh Kumar,Rafael C Nunes

doi:10.1140/epjc/s10052-021-08925-z

Abstract

Gaussian processes (GP) provide an elegant and model-independent method for extracting cosmological information from the observational data. In this work, we employ GP to perform a joint analysis by using the geometrical cosmological probes such as Supernova Type Ia (SN), Cosmic chronometers (CC), Baryon Acoustic Oscillations (BAO), and the H0LiCOW lenses sample to constrain the Hubble constant H_0, and reconstruct some properties of dark energy (DE), viz., the equation of state parameter w, the sound speed of DE perturbations c^2_s, and the ratio of DE density evolution X = rho _mathrm{de}/rho _mathrm{de,0}. From the joint analysis SN+CC+BAO+H0LiCOW, we find that H_0 is constrained at 1.1% precision with H_0 = 73.78 pm 0.84 hbox {km} hbox {s}^{-1},hbox {Mpc}^{-1}, which is in agreement with SH0ES and H0LiCOW estimates, but in sim 6.2 sigma tension with the current CMB measurements of H_0. With regard to the DE parameters, we find c^2_s < 0 at sim 2 sigma at high z, and the possibility of X to become negative for z > 1.5. We compare our results with the ones obtained in the literature, and discuss the consequences of our main results on the DE theoretical framework.

Highlights

Theoretical problems [6,7,8], which motivate alternative considerations that can explain the data and have some theoretical appeal as well
Assuming the cold dark matter (CDM) scenario, Planck-CMB data analysis provides H0 = 67.4 ± 0.5 km s−1 Mpc−1 [12], which is in 4.4σ tension with a cosmological model-independent local measurement H0 = 74.03 ± 1.42 km s−1 Mpc−1 [13] from the Hubble Space Telescope (HST) observations of 70 long-period Cepheids in the Large Magellanic Cloud
The Gaussian process (GP) is a non-parametric strategy because it does not depend on a set of free parameters of the particular model to be constrained, it depends on the choice of the covariance function, which will be explained in more detail

Summary

Introduction

Our main aim is to employ GP to perform a joint analysis by using the geometrical cosmological probes such as Supernova Type Ia (SN), Cosmic chronometers (CC), Baryon Acoustic Oscillations (BAO), and the H0LiCOW lenses sample to constrain the Hubble constant H0, and reconstruct some properties of DE, viz., the equation of state parameter w, the sound speed of DE perturbations cs, and the ratio of DE density evolution X = ρde/ρde,0 These are the main quantities that can represent the physical characteristics of DE, and possible deviations from the standard values w = −1, cs2 = 1 and X = 1, can be an indication of a new physics beyond the CDM model.

Gaussian processes

Data sets

Results and discussions

The time-delay distance in H0LiCOW sample is quantified as

Final remarks