2019ApJ...886L..23L

Strongly lensed quasar systems with time delay measurements provide "time delay distances," which are a combination of three angular diameter distances and serve as powerful tools to determine the Hubble constant H₀. However, current results often rely on the assumption of the ΛCDM model. Here we use a model-independent method based on Gaussian process to directly constrain the value of H₀. By using Gaussian process regression, we can generate posterior samples of unanchored supernova distances independent of any cosmological model and anchor them with strong lens systems. The combination of a supernova sample with large statistics but no sensitivity to H₀ with a strong lens sample with small statistics but H₀ sensitivity gives a precise H₀ measurement without the assumption of any cosmological model. We use four well-analyzed lensing systems from the state-of-art lensing program H0LiCOW and the Pantheon supernova compilation in our analysis. Assuming the universe is flat, we derive the constraint H₀ = 72.2 ± 2.1 km s^–1 Mpc^–1, a precision of 2.9%. Allowing for cosmic curvature with a prior of Ω_k = [-0.2, 0.2], the constraint becomes H₀=73.0_–3.0^+2.8kms^–1Mpc^–1.