SLICE: SPT-CL J0546-5345—A Prominent Strong-lensing Cluster at z = 1.07

Massive galaxy clusters act as prominent strong lenses. Due to a combination of observational biases, cluster evolution, and lensing efficiency, most of the known cluster lenses lie typically at zl ∼ 0.2–0.7, with only a few prominent examples at higher redshifts. Here we report the first strong-lensing analysis of the massive galaxy cluster SPT-CL J0546-5345 at a redshift zl = 1.07. This cluster was first detected through the Sunyaev–Zel’dovich effect, with a high estimated mass for its redshift of M200,c = (7.95 ± 0.92) × 1014 M⊙. Using recent JWST/NIRCam and archival Hubble Space Telescope imaging, we identify at least 10 secure and 6 candidate sets of multiply imaged background galaxies, which we use to constrain the mass distribution in the cluster. We derive effective Einstein radii of θE = 18 .″ 1 ± 1 .″ 8 for a source at zs = 3 and θE = 27 .″ 9 ± 2 .″ 8 for a source at zs = 9. The total projected mass within a 200 kpc radius around the strong-lensing region is M (