A cosmographic analysis using DESI-DR2 and strong lensing: I. Time-Delay measurements

TL;DR

This paper combines strong lensing time-delay measurements with supernova, BAO, and DESI-DR2 data to perform a model-independent cosmographic analysis, constraining universe geometry and expansion parameters.

Contribution

It introduces a novel combination of datasets for cosmography, providing new constraints on universe curvature and expansion without assuming a specific cosmological model.

Findings

Preference for an open universe with SGL+SN datasets

Constraints tighten and shift toward closed universe when including DESI-DR2

Best-fit parameters align with ΛCDM within 95-99% confidence

Abstract

Strong gravitational lensing time-delay measurements, together with the distance sum rule (DSR), offer a model-independent approach to probe the geometry and expansion of the universe without relying on a fiducial cosmological model. In this work, we perform a cosmographic analysis by combining the latest Type Ia supernova datasets (PantheonPlus, DESY5, and Union3), baryon acoustic oscillation data from DESI-DR2, and updated time-delay distances from strong lensing systems. The analyses using SGL with individual SNIa datasets (SGL+PantheonPlus, SGL+DESY5, and SGL+Union3) indicate a preference for an open universe, though they remain consistent with spatially flat universe at the $95%$ confidence level. When DESI-DR2 data is included in each combination, the constraints tighten and shift slightly toward a closed universe, while flatness remains supported at the $68%$ confidence level. The best-fit values of $q_0$ and $j_0$ agree with $\Lambda$CDM expectations within $95%$ or $99%$ confidence depending on the dataset, whereas $s_0$ remains weakly constrained in all cases. This work is the first in a series of two companion papers on cosmography with DESI-DR2 and strong lensing.