James Webb Space Telescope Feed Post

JWST Photometry of Globular Cluster Populations in Abell 2744 at z=0.3 Published: 7/26/2023 9:00:00 PM Updated: 9/22/2023 5:09:05 PM

Paper abstract: JWST imaging of the rich galaxy cluster Abell 2744 at z=0.308 has been usedby the UNCOVER team (Bezanson et al. 2022) to construct mosaic images in theNIRCAM filters. The exceptionally deep images in the (F115W, F150W,F200W) bands reveal a large population of unresolved pointlike sources acrossthe field, the vast majority of which are globular clusters (GCs). To thelimits of our photometry, more than 10,000 such objects were measured, most ofwhich are in the halos of the five largest A2744 galaxies but which alsoinclude GCs around some satellite galaxies and throughout the IntraClusterMedium. Their luminosity function follows a lognormal shape, with the datareaching to within one magnitude of the classic GCLF turnover point. The colourindex (F115W-F200W) in particular covers a range of 0.5 mag, clearlyresolving the expected internal spread of GC metallicities. The estimated GCmasses are systematically higher than in present-day galaxies, consistent witha large, normal GC population seen at a 3.5~Gyr earlier stage of dynamicalevolution. Lastly, the spatial distribution of the bluer (more metal-poor) GCsresembles the gravitational lensing map of the cluster, consistent with recenttheoretical suggestions.