A first GLIMPSE into star-cluster populations across cosmic time
Year: 2026
Type: article
Abstract: We present the first sample of 218 high-redshift ( z > 0.5) star clusters, detected with JWST/NIRCam in 78 magnified galaxies from different galaxy cluster fields. The majority of the systems (~60%) are observed in the very deep NIRCam observations of the cluster AbellS1063 (GLIMPSE program), showing the power that deep observations, combined with lensing, has to reveal these primordial stellar structures. We performed simultaneous size–flux estimates in all available NIRCam filters and spectral energy distribution (SED) fitting analysis to recover star-cluster physical properties. All star-cluster candidates have very high magnification (µ>10). Star clusters and clumps show similar ages and redshift distributions, although noticeable differences are seen in their masses, sizes and stellar surface densities inherent to the lack of resolution in the latter group. We reconstructed the formation redshift of star clusters and find that the vast majority of the observed star clusters show young ages (<100 Myr) and seem to have formed at cosmic noon (CN; 1 < z < 4). A small sample of CN star clusters are about 1 Gyr old; these potential globular clusters formed well within cosmic reionization. Star clusters have stellar densities in the range of 10 2 to 10 6 M ⊙ /pc 2 , with median values around 10 4 M ⊙ /pc 2 . Their sizes and densities better overlap with those of nuclear star clusters in the local Universe. These intrinsic properties make high-z star clusters a viable channel to grow intermediate-mass black holes. We used Bayesian inference to make the first direct measurement of the starcluster mass function at z > 1 based on a subsample of 60 star clusters younger than 100 Myr and with masses above 2 × 10 6 M ⊙ . The star cluster mass function is well described by a power law with a slope of β 50% = −1.89 −0.12 +0.13 , suggesting that a power-law -2 function might already be in place in the distant Universe.
Source: Astronomy and Astrophysics
Institutions: Lyon 1 Université, École Normale Supérieure de Lyon, Centre National de la Recherche Scientifique, Centre de Recherche Astrophysique de Lyon, Stockholm University, AlbaNova, The University of Texas at Austin, Durham University, University of Geneva, Institut d'Astrophysique de Paris, Sorbonne Université, Tufts University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
OpenAlex ID: W7203822783