Globular cluster formation with multiple stellar populations: A comprehensive overview of a star-cloud interaction scenario
Year: 2026
Type: article
Abstract: We present a new scenario for globular cluster (GC) formation with multiple stellar populations, in which both the first and second populations (1P and 2P) form from growing giant molecular clouds (GMCs) polluted by surrounding asymptotic giant branch (AGB) stars. Unlike previous AGB-polluter scenarios, this star-cloud interaction framework alleviates the mass-budget and dilution-timing problems. Idealised analytic models reproduce the observed dependence of the 1P fraction and helium abundance spread on GC mass, and qualitatively reproduce the Na-O, C-N, and Mg-Al anticorrelations and Si-Al and Mg-isotope correlations. The Mg-K anticorrelation can be reproduced only if super-AGB stars contribute significantly to GMC enrichment. The weak dependence of Li abundances on [Na/Fe] and [Al/Fe] is reproduced when about 20% of the polluting AGB stars produce Li-rich ejecta, disfavouring models in which the polluters cannot produce Li. Iron-complex Type-II GCs can form through mergers of two GCs born from separate GMCs within a dwarf galaxy at different epochs. The scenario implies that young massive clusters formed at surface star-formation-rate densities well below 1M⊙ yr−1 kpc−2 are unlikely to develop multiple stellar populations, and predicts low 12C/13C ratios (≈5) in 2P stars, a [Na/Fe]-[F/Fe] anticorrelation, and P-rich stars with [P/Fe] >0.5 and [N/Fe]>0.5. We test these predictions against more than 30 observed properties of GCs with multiple stellar populations, representing one of the most comprehensive observational benchmarks against a specific GC formation scenario to date.
Authors: Kenji Bekki, Madeleine McKenzie
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,046
Awards: G433322167, G58316358, G6273510985
OpenAlex ID: W7166706319