Paper
An Active Galaxy Cluster Merger at Cosmic Noon Revealed by JWST Weak Lensing and Multiwavelength Probes
Authors
Zachary P. Scofield, Kyle Finner, Hyungjin Joo, M. James Jee, Wonki Lee, Sangjun Cha, Jinhyub Kim, Yu-Heng Lin, Ranga-Ram Chary, Andreas Faisst, Bomee Lee
Abstract
The galaxy cluster XLSSC 122 is a rare system at , hosting surprisingly evolved member galaxies when the Universe was only one-third of its present age. Leveraging deep JWST/NIRCam imaging, we perform a weak-lensing analysis and reconstruct the cluster's mass distribution, finding a mass peak that coincides with both the X-ray peak and the position of the brightest cluster galaxy. We obtain mass and concentration estimates of and , respectively, in agreement with recent strong-lensing estimates. The high concentration in particular motivates tests against empirical and simulation-derived mass--concentration relations. Placing our weak-lensing mass map in the context of Chandra X-ray data, MeerKAT radio imaging, ALMA+ACA/ACT Sunyaev-Zel'dovich (SZ) mapping, and a new JWST intracluster light measurement, we identify consistent NE--SW elongation across datasets and a pronounced offset along the same axis between the SZ and mass/X-ray peaks, pointing to significant merger activity. XLSSC 122 thus serves as a JWST pilot study for high- lensing, demonstrating the telescope's unique ability to map cluster mass distributions at and motivating a uniform sample of analogous systems with joint lensing, X-ray, SZ, and radio data to probe cluster assembly at Cosmic Noon.