Oral Presentation

The Most Distant Strong-Lensing Cluster: Gravitational Lensing Analysis of XLSSC 122 at z=1.98

Author(s): Zachary Scofield (Yonsei University), Kyle Finner (IPAC), Sangjun Cha (Yonsei University), James Jee (Yonsei University, UC Davis), Hyungjin Joo (Yonsei University), Hyosun Park (Yonsei University)

Presenter: Zachary Scofield (Yonsei University)

The galaxy cluster XLSSC 122 at z=1.98 offers a rare glimpse into the final phase of hierarchical structure formation in the ΛCDM model. Observed as it appeared when the Universe was a third of its current size, and only three billion years after the Big Bang, this system can provide key constraints on models of structure growth and the timeline of cluster assembly. When observed with the JWST, this cluster exhibits two features previously absent in HST imaging: strong-lensing arcs and extended intracluster light (ICL). The strong-lensing detection provides a unique probe into one of the densest regions in the early universe, and when combined with the striking ICL signal and a dense weak-lensing dataset, enables a comprehensive investigation of the cluster's mass distribution and formation history. Preliminary modeling suggests that XLSSC 122 may have a higher-than-expected concentration, potentially challenging predictions from standard ΛCDM structure formation models.