TDCOSMO

XX. WFI2033–4723, the first quadruply imaged quasar modeled with JWST imaging

¹ Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095, USA
² Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794, USA
³ Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637, USA
⁴ Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637, USA
⁵ Center for Astronomy, Space Science and Astrophysics, Independent University, Bangladesh, Dhaka 1229, Bangladesh
⁶ Research Center for the Early Universe, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
⁷ IPAC, California Institute of Technology, Pasadena, CA 91125, USA
⁸ Space Telescope Science Institute, Baltimore, MD 21218, USA

^⋆ Corresponding author: devon@astro.ucla.edu

Received: 3 March 2025
Accepted: 8 July 2025

Abstract

Gravitational time delays offer unique, independent measurements of the Hubble constant, H₀. Precise measurements of H₀ stand as one of the most pressing challenges in modern cosmology, and obtaining them with time delays requires precise lens models. While much work has focused on streamlining the modeling process to keep pace with the erumpent discovery of strongly lensed systems, a critical step toward reducing uncertainty in H₀ involves increasing the precision of individual lens models themselves. In this work, we demonstrate that the unprecedented imaging capabilities of JWST make this goal attainable. We present the first lens model for time-delay cosmography derived from JWST data, applied to the quadruply imaged quasar WFI2033–4723. While the primary source of systematic uncertainty in time-delay cosmography is currently the mass-sheet degeneracy (MSD), the sensitivity of models to this MSD varies depending how the point spread function (PSF) errors are mitigated. As the PSF is also the primary source of uncertainty in lens modeling, we focus on a comparison of different PSF modeling methods. Within the context of power-law models, we recover results in agreement with previous Hubble Space Telescope (HST)-based models, but with better precision of key lensing parameters through the implementation of new PSF modeling techniques. Despite the record-holding precision of this system’s HST modeling, we were able to achieve an additional 22% increase in precision of the Fermat potential difference, thus directly reducing uncertainties of cosmological inference. These results would produce a 3% (1σ of the lens modeling error) shift of H₀ toward a higher value for this lens, if one were to keep all else constant. This work substantiates the groundbreaking potential of JWST for time-delay cosmography and lays the groundwork for modeling systems previously too faint to provide meaningful constraints on H₀.