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TDCOSMO: XX. WFI2033--4723, the First Quadruply-Imaged Quasar Modeled with JWST Imaging

D. M. Williams, T. Treu, S. Birrer, A. J. Shajib, K. C. Wong, T. Morishita, T. Schmidt, M. Stiavelli

TL;DR

This work demonstrates that JWST imaging, paired with STARRED PSF reconstruction and Lenstronomy-based modeling, can attain sub-2% precision in time-delay cosmography for the quad WFI2033--4723, surpassing HST performance and tightly constraining the perturber population and external shear. By explicitly modeling the PSF, employing a PEMD mass profile with kinematic constraints, and using rigorous model weighting across 24 configurations, the study achieves tighter Fermat-potential differences and reduces cosmographic uncertainties. The analysis confirms JWST's potential to break degeneracies—especially the mass-sheet and slope–distance degeneracies—through high-resolution arcs and robust velocity-dispersion priors, while highlighting the importance of environment and line-of-sight effects. The results justify applying JWST to a larger sample of time-delay lenses and set the stage for future cosmographic inferences that will benefit from larger, fainter lens samples from upcoming surveys.

Abstract

Gravitational time delays offer unique, independent measurements of the Hubble constant, $H_0$. Precise measurements of $H_0$ stand as one of the most pressing challenges in modern cosmology, and to do so 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 $H_0$ comes from 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 on 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 implementation of new PSF modeling techniques. Despite the record-holding precision of this system's HST modeling, we achieve an additional 22% increase in precision of the Fermat potential difference, directly reducing uncertainties of cosmological inference. These results would produce a 3% ($1σ$ of the modeling error) shift of $H_0$ towards a higher value for this lens, keeping 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 $H_0$.

TDCOSMO: XX. WFI2033--4723, the First Quadruply-Imaged Quasar Modeled with JWST Imaging

TL;DR

This work demonstrates that JWST imaging, paired with STARRED PSF reconstruction and Lenstronomy-based modeling, can attain sub-2% precision in time-delay cosmography for the quad WFI2033--4723, surpassing HST performance and tightly constraining the perturber population and external shear. By explicitly modeling the PSF, employing a PEMD mass profile with kinematic constraints, and using rigorous model weighting across 24 configurations, the study achieves tighter Fermat-potential differences and reduces cosmographic uncertainties. The analysis confirms JWST's potential to break degeneracies—especially the mass-sheet and slope–distance degeneracies—through high-resolution arcs and robust velocity-dispersion priors, while highlighting the importance of environment and line-of-sight effects. The results justify applying JWST to a larger sample of time-delay lenses and set the stage for future cosmographic inferences that will benefit from larger, fainter lens samples from upcoming surveys.

Abstract

Gravitational time delays offer unique, independent measurements of the Hubble constant, . Precise measurements of stand as one of the most pressing challenges in modern cosmology, and to do so 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 comes from 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 on 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 implementation of new PSF modeling techniques. Despite the record-holding precision of this system's HST modeling, we achieve an additional 22% increase in precision of the Fermat potential difference, directly reducing uncertainties of cosmological inference. These results would produce a 3% ( of the modeling error) shift of towards a higher value for this lens, keeping 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 .

Paper Structure

This paper contains 52 sections, 40 equations, 12 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Outline of analysis
  3. Theory and observables
  4. Additional sources of error and degeneracies
  5. Internal mass sheet degeneracy
  6. Multiplane lensing
  7. External convergence
  8. Mass density slope and time-delay distance degeneracy
  9. Analysis of kinematics
  10. Bayesian analysis
  11. Data
  12. WFI2033--4723
  13. JWST imaging
  14. Spectroscopic data
  15. Wide-field photometric data and external convergence
  16. ...and 37 more sections

Figures (12)

  • Figure 1: JWST NIRCam color image of WFI2033-4723 (GTO Program #1198; PI: Stiavelli). The F115W band is mapped to the luminosity and blue, F150W to cyan, F277W to yellow, and the F356W band to red. Near the bottom image, there is a bright spot on the lower-right side that maps back to other bluer regions of the ring, indicating it is a multiply imaged star-forming region contained in the z$\sim\!1.6$ host. Preliminary models place the physical size at $\sim\!150$pc and locate it at $\sim\!2$kpc from the center of the galaxy (assuming a flat CDM cosmology with h = 0.7 and m = 0.3).
  • Figure 2: Comparison of the JWST data used in this analysis, NIRCam F115W, to the HST imaging, ACS/F814W. The ring structure is maximized in each visualization, as it provides the tightest constraints on the deflector's radial mass profile.
  • Figure 3: Environment of WFI2033. Black labels denote the main deflector (D), its nearby satellite (X), and the three galaxy perturbers (G2, G3, and G7) along with their redshifts. The quasar images are labeled in blue.
  • Figure 4: Comparison of the PSF kernels used. First we show the STARRED initial PSF kernel, and it is followed by an example of an updated PSF from one of the STARRED models. Then we show the PSFr initial PSF kernel, which is again followed by an example of an updated PSF from a PSFr model.
  • Figure 5: Example model output from the best performing model shown in \ref{['tab:res_mods']}. We note that the other models are qualitatively indistinguishable. The top-left panel shows the observed image, the top-middle panel shows the model-predicted reconstruction of the image, and top-right panel shows the fit's residuals normalized by the estimated uncertainty of each pixel (see \ref{['ssec:psf_noise_estimation']} for more details). At the bottom left is the reconstructed source plot, featuring more detail than any parametric source modeled for time-delay cosmography thus far. The star symbol denotes the location of the quasar host galaxy's centroid. The bottom-middle panel shows the lensed unconvolved extended-source light, and the bottom-right panel shows the magnification map of the system.
  • ...and 7 more figures