Cosmic Equation of state from Strong Gravitational Lensing Systems

TL;DR

This paper uses strong gravitational lensing systems to constrain the cosmic equation of state, combining lensing geometry with stellar kinematics, and finds results consistent with previous studies while highlighting systematic deviations and selection effects.

Contribution

It introduces a method combining lensing and stellar kinematics to estimate the cosmic equation of state, demonstrating its consistency and potential for future larger surveys.

Findings

Results agree with existing literature on cosmic equation of state.

Identifies systematic deviations between standard candles and rulers.

Highlights a key selection effect related to lensing geometry.

Abstract

Accelerating expansion of the Universe is a great challenge for both physics and cosmology. In light of lacking the convincing theoretical explanation, an effective description of this phenomenon in terms of cosmic equation of state turns out useful. The strength of modern cosmology lies in consistency across independent, often unrelated pieces of evidence. Therefore, every alternative method of restricting cosmic equation of state is important. Strongly gravitationally lensed quasar-galaxy systems create such new opportunity by combining stellar kinematics (central velocity dispersion measurements) with lensing geometry (Einstein radius determination form position of images). In this paper we apply such method to a combined data sets from SLACS and LSD surveys of gravitational lenses. In result we obtain the cosmic equation of state parameters, which generally agree with results already known in the literature. This demonstrates that the method can be further used on larger samples obtained in the future. Independently noticed systematic deviation between fits done on standard candles and standard rulers is revealed in our findings. We also identify an important selection effect crucial to our method associated with geometric configuration of the lensing system along line of sight, which may have consequences for sample construction from the future lensing surveys.