Disentangling the dark and stellar mass through precise lens modelling of the JWST observation of lensed quasar WFI2033–4723
- 1Institute of Cosmology and Gravitation, University of Portsmouth , Burnaby Rd, Portsmouth PO1 3FX ,
- 2University of Geneva Department of Astronomy, , Chemin d’Ecogia 16, 1290 Versoix ,
Abstract
We use high-resolution JWST/NIRCam imaging and measured time delays to model the quadruply imaged quasar WFI2033–4723 with a composite stellar plus dark-matter mass model. We first construct an elliptical power-law baseline model and recover Fermat-potential differences (fpd) consistent with previous HST-based and JWST-based analyses, providing a reference scale for composite modelling. We then replace the total mass profile with a physically motivated decomposition in which the stellar mass follows a multi-Gaussian expansion of the lens light, with a free radial mass-to-light gradient, and the dark matter is described by a generalized Navarro–Frenk–White (gNFW) halo. Using two external cosmological priors, Planck+DESI and Pantheon+SH0ES, the measured time delays constrain the mass-sheet-transformation freedom that would otherwise damage the stellar–dark-matter decomposition. In both cosmological cases, the stellar normalization lies between the expectations for Chabrier and Salpeter initial mass functions, while the radial mass-to-light gradient is not strongly required by the data (mildly positive). The dark matter halo has an inner slope γin ≃ 1.3, steeper than a standard NFW cusp, and the main astrophysical conclusions are insensitive to the adopted cosmological prior. This work shows that composite time-delay lens modelling can effectively separate baryons from dark matter. As a qualitative check, we reverse the logic and use our composite lens model without kinematic information to infer the cosmology instead. However, the strong degeneracy between H0 and the halo scale radius Rs prevents a robust standalone constraint.
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BibTeX
@article{li2026disentangling,
title = {{Disentangling the dark and stellar mass through precise lens modelling of the JWST observation of lensed quasar WFI2033–4723}},
author = {Tian Li and Thomas E Collett and Coleman M Krawczyk and Wolfgang J R Enzi and Aymeric Galan},
journal = {Monthly Notices of the Royal Astronomical Society},
year = {2026},
month = oct,
doi = {10.1093/mnras/stag1986},
url = {https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag1986/8943795},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Disentangling the dark and stellar mass through precise lens modelling of the JWST observation of lensed quasar WFI2033–4723
AU - Tian Li
AU - Thomas E Collett
AU - Coleman M Krawczyk
AU - Wolfgang J R Enzi
AU - Aymeric Galan
PY - 2026
DA - 2026/10/19
JO - Monthly Notices of the Royal Astronomical Society
DO - 10.1093/mnras/stag1986
UR - https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag1986/8943795
AB - We use high-resolution JWST/NIRCam imaging and measured time delays to model the quadruply imaged quasar WFI2033–4723 with a composite stellar plus dark-matter mass model. We first construct an elliptical power-law baseline model and recover Fermat-potential differences (fpd) consistent with previous HST-based and JWST-based analyses, providing a reference scale for composite modelling. We then replace the total mass profile with a physically motivated decomposition in which the stellar mass follows a multi-Gaussian expansion of the lens light, with a free radial mass-to-light gradient, and the dark matter is described by a generalized Navarro–Frenk–White (gNFW) halo. Using two external cosmological priors, Planck+DESI and Pantheon+SH0ES, the measured time delays constrain the mass-sheet-transformation freedom that would otherwise damage the stellar–dark-matter decomposition. In both cosmological cases, the stellar normalization lies between the expectations for Chabrier and Salpeter initial mass functions, while the radial mass-to-light gradient is not strongly required by the data (mildly positive). The dark matter halo has an inner slope γin ≃ 1.3, steeper than a standard NFW cusp, and the main astrophysical conclusions are insensitive to the adopted cosmological prior. This work shows that composite time-delay lens modelling can effectively separate baryons from dark matter. As a qualitative check, we reverse the logic and use our composite lens model without kinematic information to infer the cosmology instead. However, the strong degeneracy between H0 and the halo scale radius Rs prevents a robust standalone constraint.
SN - 0035-8711
SN - 1365-2966
ER -