A tight relation between the distribution of globular clusters and dark matter in AS1063

¹ Instituto de Física de Cantabria (CSIC-UC), Avda. Los Castros s/n., 39005 Santander, Spain
² Jodrell Bank Centre for Astrophysics, Alan Turing Building, University of Manchester, Oxford Road, Manchester M13 9PL, UK

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 23 February 2026
Accepted: 9 April 2026

Abstract

Based on deep high-resolution JWST images of AS1063, and after a careful masking of artifacts, extended features in the cluster, and background galaxies (including known lensed ones), we have identified tens of thousands of unresolved point sources in the central region of the galaxy cluster. We extended the identification of these point sources up to 1.18 Mpc from the center of the cluster using data in the second module. Most of these sources are expected to be globular clusters orbiting in the deep potential well of the cluster, but also the surviving compact cores of satellite galaxies. We studied the distribution of the globular clusters and compared it with the distribution of mass from a lens model derived from the same JWST data. We find a very tight correlation between the two distributions, but also some differences, including a more concentrated distribution for the globular clusters than for dark matter. We explored the possibility of using the distribution of globular clusters as a proxy for the lensing mass. We find that a simple smoothing kernel can transform the discrete distribution of point sources into a continuous two-dimensional distribution that closely matches the lensing convergence. This suggests that globular clusters can be used as tracers of the dark matter distribution in other massive clusters where gravitational lensing constraints are scarce but globular clusters can be detected more easily; for instance, in low-redshift galaxy clusters.