Globular Clusters in the Galaxy Cluster MACS0416 at z = 0.397

TL;DR

This study uses JWST imaging to analyze globular clusters in a galaxy cluster at z=0.397, revealing their ages, metallicities, and luminosity distribution, and identifying potential ultra-compact dwarf systems.

Contribution

First detailed photometric analysis of globular clusters in MACS J0416 at intermediate redshift using JWST data, providing insights into their properties and evolution.

Findings

Globular clusters are mostly 5-9 Gyr old with a wide metallicity range.

The globular cluster luminosity function is log-normal and truncated at faint magnitudes.

Some sources may be ultra-compact dwarf galaxies or stripped nuclei.

Abstract

We present a photometric analysis of globular clusters (GCs) in the massive galaxy cluster MACS J0416.1-2403 (z = 0.397) using deep JWST/NIRCam imaging from the PEARLS program. PSF photometry was performed in the short wavelength filters F090W, F115W, F150W, and F200W, yielding a catalog of approximately 3 x 10^3 unresolved, point-like sources consistent with a GC population. Artificial star tests indicate 80% completeness at F200W = 30.36 mag. The color-magnitude diagrams show a narrow GC sequence well reproduced by PARSEC single-stellar-population models spanning ages of 5-9 Gyr and metallicities from [M/H] = -2.0 to +0.2, consistent with evolved GC systems at this redshift. The globular cluster luminosity function (GCLF) follows a log-normal form truncated by incompleteness at the faint end. The brightest sources extend slightly beyond the locus of classical GCs, suggesting a small number of UCD-like systems or stripped nuclei, while the bulk of the population exhibits the luminosities and colors expected for mature globular clusters at z ~ 0.4.