Probing the course of cosmic expansion with a combination of observational data

TL;DR

This study reconstructs the cosmic expansion history using multiple observational data sets and dark energy models, revealing that conclusions about acceleration depend on data analysis methods and model parametrizations.

Contribution

It introduces a comprehensive reconstruction of cosmic expansion history combining diverse observational data and compares different dark energy parametrizations and supernova light curve fits.

Findings

MLCS2k2 data suggests slowing-down acceleration with certain models

Results vary significantly with light curve fitting methods and dark energy parametrizations

The evolution of dark energy and acceleration depends on analysis choices

Abstract

We study the cosmic expansion history by reconstructing the deceleration parameter $q(z)$ from the SDSS-II type Ia supernova sample (SNIa) with two different light curve fits (MLCS2k2 and SALT-II), the baryon acoustic oscillation (BAO) distance ratio, the cosmic microwave background (CMB) shift parameter, and the lookback time-redshift (LT) from the age of old passive galaxies. Three parametrization forms for the equation of state of dark energy (CPL, JBP, and UIS) are considered. Our results show that, for the CPL and the UIS forms, MLCS2k2 SDSS-II SNIa+BAO+CMB and MLCS2k2 SDSS-II SNIa+BAO+CMB+LT favor a currently slowing-down cosmic acceleration, but this does not occur for all other cases, where an increasing cosmic acceleration is still favored. Thus, the reconstructed evolutionary behaviors of dark energy and the course of the cosmic acceleration are highly dependent both on the light curve fitting method for the SNIa and the parametrization form for the equation of state of dark energy.