2024/02/12 by G. Parmentier, Parmentier, Geneviève · 1 citation
Physics and Astronomy · #Astro and Planetary Science #Astronomical and nuclear sciences #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2402.07979
openalex publication_date 2024/02/12 · openalex created_date 2024/02/15 · openalex updated_date 2026/07/28
The phenomenon of multiple stellar populations is exacerbated in massive globular clusters, with the fraction of first-population (1P) stars a decreasing function of the cluster present-day mass. We decipher this relation in far greater detail than has been done so far. We assume (i) a fixed stellar mass threshold for the formation of second-population (2P) stars, (ii) a power-law scaling F1P ∝ mecl-1 between the mass mecl of newly-formed clusters and their 1P-star fraction F1P, and (iii) a constant F1P over time. The F1P(mecl) relation is then evolved up to an age of 12Gyr for tidal field strengths representative of the entire Galactic halo. The 12Gyr-old model tracks cover extremely well the present-day distribution of Galactic globular clusters in (mass,F1P) space. The distribution is curtailed on its top-right side by the scarcity of clusters at large Galactocentric distances, and on its bottom-left side by the initial scarcity of very high-mass clusters, and dynamical friction. Given their distinct dissolution rates, "inner" and "outer" model clusters are offset from each other, as observed. The locus of Magellanic Clouds clusters in (mass,F1P) space is as expected for intermediate-age clusters evolving in a gentle tidal field. Given the assumed constancy of F1P, we conclude that 2P-stars do not necessarily form centrally-concentrated. We infer a minimum mass of 4 ⋅ 105~M\odot for multiple-populations clusters at secular evolution onset. This high-mass threshold severely limits the amount of 2P-stars lost from evolving clusters, thereby fitting the low 2P-star fraction of the Galactic halo field.