A measurement of the Hubble constant from angular diameter distances to two gravitational lenses

TL;DR

This paper measures the Hubble constant by calibrating supernova distances with angular diameter distances to two gravitational lenses, providing an independent estimate of the Universe's expansion rate.

Contribution

It introduces a method using gravitational lens distances as a weakly cosmology-dependent calibrator for supernova-based Hubble constant measurements.

Findings

Hubble constant estimated as 82.4 km/s/Mpc with uncertainties

Angular diameter distances to lenses determined at specific redshifts

Calibration of supernova distances using lens measurements

Abstract

The local expansion rate of the Universe is parametrized by the Hubble constant, $H_0$, the ratio between recession velocity and distance. Different techniques lead to inconsistent estimates of $H_0$. Observations of Type Ia supernovae (SNe) can be used to measure $H_0$, but this requires an external calibrator to convert relative distances to absolute ones. We use the angular diameter distance to strong gravitational lenses as a suitable calibrator, which is only weakly sensitive to cosmological assumptions. We determine the angular diameter distances to two gravitational lenses, $810^{+160}_{-130}$ and $1230^{+180}_{-150}$~Mpc, at redshifts of $z=0.295$ and $0.6304$. Using these absolute distances to calibrate 740 previously-measured relative distances to SNe, we measure the Hubble constant to be $H_0=82.4^{+8.4}_{-8.3} ~{\rm km\,s^{-1}\,Mpc^{-1}}$.