Comparison of cosmological models using standard rulers and candles

TL;DR

This study compares five dark energy models using standard rulers and candles, incorporating a generalized mass density profile for strong lensing, and finds the cosmological constant remains the most supported model.

Contribution

It introduces a joint analysis of standard rulers and candles with a generalized lensing profile, relaxing previous assumptions and providing more restrictive cosmological constraints.

Findings

Best-fit gamma parameters are consistent across models.

Combination of data sets yields tighter parameter constraints.

Results favor the cosmological constant model over alternatives.

Abstract

In this paper, we used standard rulers and standard candles (separately and jointly) to explore five popular dark energy models under assumption of spatial flatness of the Universe. As standard rulers, we used a data set comprising 118 galactic-scale strong lensing systems (individual standard rulers if properly calibrated for the mass density profile) combined with BAO diagnostics (statistical standard ruler). Supernovae Ia served asstandard candles. Unlike in the most of previous statistical studies involving strong lensing systems, we relaxed the assumption of singular isothermal sphere (SIS) in favor of its generalization: the power-law mass density profile. Therefore, along with cosmological model parameters we fitted the power law index and its first derivative with respect to the redshift (thus allowing for mass density profile evolution). It turned out that the best fitted $\gamma$ parameters are in agreement with each other irrespective of the cosmological model considered. This demonstrates that galactic strong lensing systems may provide a complementary probe to test the properties of dark energy. Fits for cosmological model parameters which we obtained are in agreement with alternative studies performed by the others. Because standard rulers and standard candles have different parameter degeneracies, combination of standard rulers and standard candles gives much more restrictive results for cosmological parameters. At last, we attempted at model selection based on information theoretic criteria (AIC and BIC). Our results support the claim, that cosmological constant model is still the best one and there is no (at least statistical) reason to prefer any other more complex model.