Simulations of Globular Clusters Within Their Parent Galaxies: Metallicity Spreads and Anomalous Precursor Populations
Speakers: Toby Devereaux (Università degli Studi di Padova)
Recent observations of globular clusters (GCs) suggest that elemental abundance variations may exist between first-generation(1G) stars. We propose that metal abundance (‘metallicity’) spreads within GC forming giant molecular clouds (GMCs) caninfluence the iron abundances of future cluster members. To investigate this, we use original hydrodynamical simulations tomodel GMC formation in a high redshift dwarf galaxy. Our simulations self-consistently model physical processes such as stellarfeedback, dust formation and destruction, and molecular gas formation on dust grains, making them well suited to the study ofGMC formation. We conclude that iron abundance variations in GMCs are due to the merging of gas clumps and self-enrichmentprocesses. The metallicity dispersions of GC forming clumps is?0.1 dex, reflecting a growing number of studies that claim anon-zero dispersion within GCs. The galactic gas fraction is a key parameter for the formation of clumps and the metallicity‘floor’ observed for both Galactic and extra-galactic GCs are associated with the parent galaxy’s capacity to form massiveGMCs. Finally, we argue that GMCs have the potential to trap surrounding metal-poor galactic disc stars, which we interpretas a precursor population (0G). These low metallicity stars are representative of the [Fe/H] value of the host dwarf and thus thechemistry of this 0G may be a fossilised record of the parent galaxy. These results depend on the initial metallicity and radialgradient of the galaxy, the threshold gas density for star formation and the star formation prescription.