Observations of Massive Stars in Extragalactic Star Clusters

Abstract

An overview is provided of ultraviolet observations of young (≤ 10 Myr), massive(≥ 10 ⁴ M _⊙ ) extragalactic star clusters, ranging from spatially resolved clusters in the Magellanic Clouds (e.g. R136) to unresolved clusters beyond the Local Group (e.g. SSC-N in II Zw 40). Collectively these provide a rich empirical dataset across metallicity and age, with which to test spectral synthesis techniques which are widely used to study star-forming knots in galaxies on much larger scales. Overall standard tools are capable of reproducing UV spectroscopy of massive star clusters, while discrepancies highlight the need to incorporate binary star evolution plus contemporary mass-loss prescriptions for very massive stars.