Constraining cosmic curvature by using age of galaxies and gravitational lenses

TL;DR

This study employs two model-independent methods, using galaxy ages and gravitational lensing data, to constrain the universe's curvature, finding it to be marginally closed but consistent with flatness within uncertainties.

Contribution

It introduces a combined, model-independent approach using galaxy ages and gravitational lensing to constrain cosmic curvature without assuming a specific cosmological model.

Findings

The curvature parameter $\

The universe may be marginally closed, but flatness cannot be ruled out at 3σ.

The curvature remains constant over the studied redshift range.

Abstract

We use two model-independent methods to constrain the curvature of the universe. In the first method, we study the evolution of the curvature parameter ($\Omega_k^0$) with redshift by using the observations of the Hubble parameter and transverse comoving distances obtained from the age of galaxies. Secondly, we also use an indirect method based on the mean image separation statistics of gravitationally lensed quasars. The basis of this methodology is that the average image separation of lensed images will show a positive, negative or zero correlation with the source redshift in a closed, open or flat universe respectively. In order to smoothen the datasets used in both the methods, we use a non-parametric method namely, Gaussian Process (GP). Finally from first method we obtain $\Omega_k^0= 0.025\pm0.57$ for a presumed flat universe while the cosmic curvature remains constant throughout the redshift region $0<z<1.37$ which indicates that the universe may be homogeneous. Moreover, the combined result from both the methods suggests that the universe is marginally closed. However, a flat universe can be incorporated at $3\sigma$ level.