VENUS: Strong-lensing model of MACS J1931.8-2635 -- revealing the farthest multiply imaged supernova

TL;DR

This paper develops a detailed strong-lensing model for galaxy cluster MACS J1931.8-2635, successfully predicting multiple images of a high-redshift supernova, SN Eos, and demonstrating the potential of lensed supernovae for cosmography.

Contribution

The paper presents a new parametric lensing model constrained by 19 multiple-image systems, including the first detailed prediction of multiple images of a distant supernova in this cluster.

Findings

Predicted five images of SN Eos with specific magnifications and time delays.

Confirmed the transient nature of SN Eos through absence of certain predicted images.

Identified a new triply imaged spiral galaxy candidate at z~3.65.

Abstract

We present a parametric strong-lensing model for the galaxy cluster MACS J1931.8-2635 ($z_l = 0.35$), accompanying the detection of the spectroscopically confirmed SN Eos at $z = 5.13$ (Coulter et al. 2026). We identify 10 new multiple-image systems in recent VENUS JWST/NIRCam imaging, so that the model is constrained with a total of 19 robust multiple-image systems -- nine of which also have a spectroscopic redshift. For the point-like source corresponding to SN Eos, our model predicts a total of five images, with the observed radial image pair having a similar magnification of $\mu \simeq 25 - 30$ and a small time delay of $< 5$ days, in agreement with their simultaneous observation. According to the model, the other three predicted images arrived earlier, with time delays of $3.7 \pm 0.7$, $3.5 \pm 0.7$ and $54.0 \pm 10.8$ years prior to the two observed images, and with magnifications of $12.9 \pm 2.6$, $13.0 \pm 2.9$ and $2.2 \pm 0.4$, respectively. The absence of detections at the predicted positions, where the host galaxy's images are also visible, confirms the transient nature of the source. SN Eos and its host galaxy are studied in separate articles, and we here focus on the lens model. The final model reaches a very good $r.m.s.$ distance between model and observations of $0.44''$. We present the lens-modeling results, including newly identified systems such as a triply imaged, grand-design spiral galaxy candidate at $z \simeq 3.65_{-0.09}^{+0.04}$, and briefly discuss the potential of using high-redshift lensed SNe for cosmography.