Curvature from strong gravitational lensing: a spatially closed Universe or systematics?

TL;DR

This study uses model-independent methods with supernovae and gravitational lensing data to suggest a spatially closed Universe, while examining potential systematic biases affecting curvature measurements.

Contribution

It provides the first model-independent measurement of spatial curvature using the distance sum rule with recent SNe and SGL data, highlighting possible systematics.

Findings

A spatially closed Universe is preferred by the data.

Systematic biases may arise from combining different survey data.

Using specific subsamples or complex lens models reduces tension with flat Universe.

Abstract

Model-independent constraints on the spatial curvature are not only closely related to important problems such as the evolution of the Universe and properties of dark energy, but also provide a test of the validity of the fundamental Copernican principle. In this paper, with the distance sum rule in the Friedmann-Lema\^{i}tre-Robertson-Walker metric, we achieve model-independent measurements of the spatial curvature from the latest type Ia supernovae and strong gravitational lensing (SGL) observations. We find that a spatially closed Universe is preferred. Moreover, by considering different kinds of velocity dispersion and subsample, we study possible factors which might affect model-independent estimations for the spatial curvature from SGL observations. It is suggested that the combination of observational data from different surveys might cause a systematic bias and the tension between the spatially flat Universe and SGL observations is alleviated when the subsample only from the Sloan Lens ACS Survey is used or a more complex treatment for the density profile of lenses is considered.