Galaxy mass modelling from multiwavelength JWST strong lens analysis: dark matter substructure, angular mass complexity, or both?

Lange, Samuel C.; Amvrosiadis, Aristeidis; Nightingale, James W.; He, Qiuhan; Frenk, Carlos S.; Robertson, Andrew; Cole, Shaun; Massey, Richard; Cao, Xiaoyue; Li, Ran; Wang, Kaihao

Abstract

We analyse two galaxy-scale strong gravitational lenses, SPT0418-47 and SPT2147-50, using JWST NIRCam imaging across multiple filters. To account for angular complexity in the lens mass distribution, we introduce multipole perturbations with orders m = 1, 3, 4. Our results show strong evidence for angular mass complexity in SPT2147, with multipole strengths of 0.3–1.7 per cent for m = 3, 4 and 2.4–9.5 per cent for m = 1, while SPT0418 shows no such preference. We also test lens models that include a dark matter substructure, finding a strong preference for a substructure in SPT2147-50 with a Bayes factor of ▲log(ε)∼ 60 when multipoles are not included. Including multipoles reduces the Bayes factor to ▲log(ε)∼ 11, still corresponding to a 5σ detection of a subhalo with an NFW (Navarro–Frenk–White) mass of log10(M200/M☉) = 10.87+−00..7153. While SPT2147-50 may represent the fourth detection of a dark matter substructure in a strong lens, further analysis is needed to confirm that the signal is not due to systematics associated with the lens mass model.

Citation

Lange, S. C., Amvrosiadis, A., Nightingale, J. W., He, Q., Frenk, C. S., Robertson, A., Cole, S., Massey, R., Cao, X., Li, R., & Wang, K. (2025). Galaxy mass modelling from multiwavelength JWST strong lens analysis: dark matter substructure, angular mass complexity, or both?. Monthly Notices of the Royal Astronomical Society, 539(2), 704-726. https://doi.org/10.1093/mnras/staf491

• Journal Article Type: Article
• Acceptance Date: Mar 18, 2025
• Online Publication Date: Mar 28, 2025
• Publication Date: 2025-05
• Deposit Date: May 27, 2025
• Publicly Available Date: May 27, 2025
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 539
• Issue: 2
• Pages: 704-726
• DOI: https://doi.org/10.1093/mnras/staf491
• Public URL: https://durham-repository.worktribe.com/output/3964827