The Hubble constant from eight time-delay galaxy lenses

TL;DR

This study estimates the Hubble constant using eight quadruply lensing systems with a free-form analysis, finding results consistent with other measurements but highlighting current limitations in resolving the Hubble tension.

Contribution

It introduces a joint, free-form lensing analysis of multiple systems, accounting for systematic uncertainties and lensing degeneracies, providing a robust estimate of H0.

Findings

H0 = 71.8^{+3.9}_{-3.3} km/s/Mpc with 4.97% precision

Results agree with supernovae and CMB measurements

Current lensing data cannot resolve the Hubble tension

Abstract

We present a determination of the Hubble constant from the joint, free-form analysis of 8 strongly, quadruply lensing systems. In the concordance cosmology, we find $H_0 = 71.8^{+3.9}_{-3.3}\,\mathrm{km}\,\mathrm{s}^{-1}\,\mathrm{Mpc}^{-1}$ with a precision of $4.97\%$. This is in agreement with the latest measurements from Supernovae Type Ia and Planck observations of the cosmic microwave background. Our precision is lower compared to these and other recent time-delay cosmography determinations, because our modelling strategies reflect the systematic uncertainties of lensing degeneracies. We furthermore are able to find reasonable lensed image reconstructions by constraining to either value of $H_0$ from local and early Universe measurements. This leads us to conclude that current lensing constraints on $H_0$ are not strong enough to break the "Hubble tension" problem of cosmology.