2023MNRAS.522.4430S

Low-mass star formation regions are unlikely to fully populate their initial mass functions (IMFs), leading to a deficit of massive stars. In binary stellar populations, the full range of binary separations and mass ratios will also be underpopulated. To explore the effects of stochastic sampling in the integrated light of stellar clusters, we calculate models at a broad range of cluster masses, from 10² to 10⁷ M_⊙, using a binary stellar population synthesis code. For clusters with stellar masses less than 10⁵ M_⊙, observable quantities show substantial scatter and their mean properties reflect the expected deficit of massive stars. In common with previous work, we find that purely stochastic sampling of the IMF appears to underestimate the mass of the most massive star in known clusters. However, even with this constraint, the majority of clusters likely inject sufficient kinetic energy to clear their birth clusters of gas. For quantities that directly measure the impact of the most massive stars, such as N_ion, ξ_ion, and β_UV, uncertainties due to stochastic sampling dominate over those from the IMF shape or distribution of binary parameters, while stochastic sampling has a negligible effect on the stellar continuum luminosity density.