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, and Bomee Lee

Abstract

The galaxy cluster XLSSC 122 is a rare system at z = 1.98, 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. Consistent with recent strong-lensing analyses, we obtain a mass estimate of 1.60 ± 0.30 (stat.) ± 0.26 (LSS) × 1014 M⊙ and an implied concentration of c200c = 6.3 ± 0.4, where the uncertainty represents the propagation of the mass error through the adopted concentration–mass relation and excludes intrinsic scatter. Placing our weak-lensing mass map in the context of Chandra X-ray data, MeerKAT radio imaging, Atacama Large Millimeter/submillimeter Array + Atacama Compact Array/Atacama Cosmology Telescope Sunyaev–Zel’dovich (SZ) mapping, and new JWST intracluster light measurements, 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-z lensing, demonstrating the telescope’s unique ability to map cluster mass distributions at z ∼ 2. The concordance of the multiwavelength analysis here, together with the high concentration relative to ΛCDM expectations, motivates a uniform sample of analogous systems with joint lensing, X-ray, SZ, and radio data to probe cluster assembly at cosmic noon.

NASA/ADS