The impact of metallicity-dependent mass-loss versus dynamical heating on the early evolution of star clusters

• Published in: Monthly notices of the Royal Astronomical Society Vol. 445; no. 2; p. 1967
• Main Authors: Trani, A A, Mapelli, M, Bressan, A
• Format: Journal Article
• Language: English
• Published: London Oxford University Press 01-12-2014
• Subjects: Astronomy; Collapse; Encounters; Heating; Impact analysis; Massive stars; Metallicity; Metals; Simulation; Star & galaxy formation; Star clusters; Stellar evolution; Stellar winds; Supernovae
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stu1898

We have run direct N-body simulations to investigate the impact of stellar evolution and dynamics on the structural properties of young massive (~3 x 10... M...) star clusters (SCs) with different metallicities (Z = 1, 0.1, 0.01 Z...). Metallicity drives the mass-loss by stellar winds and supernovae (SNe), with SCs losing more mass at high metallicity. We have simulated three sets of initial conditions, with different initial relaxation time-scale. We find that the evolution of the half-mass radius of SCs depends on how fast two-body relaxation is with respect to the lifetime of massive stars. If core collapse is slow in comparison with stellar evolution, then mass-loss by stellar winds and SNe is the dominant mechanism driving SC evolution, and metal-rich SCs expand more than metal-poor ones. In contrast, if core collapse occurs on a comparable time-scale with respect to the lifetime of massive stars, then SC evolution depends on the interplay between mass-loss and three-body encounters: dynamical heating by three-body encounters (mass-loss by stellar winds and SNe) is the dominant process driving the expansion of the core in metal-poor (metal-rich) SCs. As a consequence, the half-mass radius of metal-poor SCs expands more than that of metal-rich ones. We also find core radius oscillations, which grow in number and amplitude as metallicity decreases. (ProQuest: ... denotes formulae/symbols omitted.)