Globular Clusters in the Time of the JWST. I. Survey Design and First Results on Multiple Populations and Beyond
Abstract
Globular clusters (GCs) host multiple stellar populations with distinct chemical compositions, but their properties among very low-mass stars remain poorly constrained. The James Webb Space Telescope (JWST) enables precise infrared studies that are highly sensitive to abundance variations in cool stars. We initiate a homogeneous survey of Galactic GCs, based primarily on deep JWST GO-8960 observations and complemented by archival JWST and Hubble Space Telescope data, to characterize multiple populations across a wide range of cluster properties. In this first paper, we present the survey and initial NIRCam results. We analyze eleven GCs, deriving high-precision photometry and astrometry to measure proper motions. Multiple populations are detected among low-mass stars in all clusters, with diverse behaviors. We find discrete main sequences in NGC 288, NGC 6723, and NGC 2808, and more continuous distributions in NGC 104 and the Type II clusters NGC 1851 and NGC 6656. The bulge clusters NGC 6528, NGC 6553, and NGC 6440 show patterns consistent with varying helium and oxygen abundances that do not scale simply with cluster mass. In Terzan 5 and Liller 1, we identify populations spanning different ages and helium variations within the old population of Terzan 5. We also detect an M-dwarf gap in NGC 104 around 0.35 solar masses, consistent with the Jao Gap of field stars and open clusters. This work establishes the foundation for a homogeneous JWST survey of Galactic GCs and provides a valuable dataset for studies of cluster evolution, Galactic stellar populations, and background extragalactic sources.
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BibTeX
@misc{milone2026globular,
title = {{Globular Clusters in the Time of the JWST. I. Survey Design and First Results on Multiple Populations and Beyond}},
author = {A. P. Milone and A. F. Marino and G. Cordoni and E. Dondoglio and M. V. Legnardi and T. Ziliotto and E. Bortolan and F. Muratore and F. D'Antona and A. Renzini and G. Girardi and L. Gorza and A. Mastrobuono-Battisti and C. Ventura and P. Ventura and V. Altomonte and L. Bisigello and Y. Cavecchi and F. Dell'Agli and A. Dotter and E. P. Lagioia and C. Li and S. Lionetto and A. Marchuk and J. Qi and G. Rodighiero and M. Tailo and H. Wirth},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2606.20979},
eprint = {2606.20979},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.20979},
}
RIS
TY - UNPB
TI - Globular Clusters in the Time of the JWST. I. Survey Design and First Results on Multiple Populations and Beyond
AU - A. P. Milone
AU - A. F. Marino
AU - G. Cordoni
AU - E. Dondoglio
AU - M. V. Legnardi
AU - T. Ziliotto
AU - E. Bortolan
AU - F. Muratore
AU - F. D'Antona
AU - A. Renzini
AU - G. Girardi
AU - L. Gorza
AU - A. Mastrobuono-Battisti
AU - C. Ventura
AU - P. Ventura
AU - V. Altomonte
AU - L. Bisigello
AU - Y. Cavecchi
AU - F. Dell'Agli
AU - A. Dotter
AU - E. P. Lagioia
AU - C. Li
AU - S. Lionetto
AU - A. Marchuk
AU - J. Qi
AU - G. Rodighiero
AU - M. Tailo
AU - H. Wirth
PY - 2026
DA - 2026/09/08
PB - arXiv
DO - 10.48550/arxiv.2606.20979
UR - https://arxiv.org/abs/2606.20979
AB - Globular clusters (GCs) host multiple stellar populations with distinct chemical compositions, but their properties among very low-mass stars remain poorly constrained. The James Webb Space Telescope (JWST) enables precise infrared studies that are highly sensitive to abundance variations in cool stars. We initiate a homogeneous survey of Galactic GCs, based primarily on deep JWST GO-8960 observations and complemented by archival JWST and Hubble Space Telescope data, to characterize multiple populations across a wide range of cluster properties. In this first paper, we present the survey and initial NIRCam results. We analyze eleven GCs, deriving high-precision photometry and astrometry to measure proper motions. Multiple populations are detected among low-mass stars in all clusters, with diverse behaviors. We find discrete main sequences in NGC 288, NGC 6723, and NGC 2808, and more continuous distributions in NGC 104 and the Type II clusters NGC 1851 and NGC 6656. The bulge clusters NGC 6528, NGC 6553, and NGC 6440 show patterns consistent with varying helium and oxygen abundances that do not scale simply with cluster mass. In Terzan 5 and Liller 1, we identify populations spanning different ages and helium variations within the old population of Terzan 5. We also detect an M-dwarf gap in NGC 104 around 0.35 solar masses, consistent with the Jao Gap of field stars and open clusters. This work establishes the foundation for a homogeneous JWST survey of Galactic GCs and provides a valuable dataset for studies of cluster evolution, Galactic stellar populations, and background extragalactic sources.
ER -