Star Clusters Across Cosmic Time Mark R. Krumholz1;2, Christopher F. McKee3, and Joss Bland-Hawthorn2;4;5 1Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia; email:
[email protected] 2Centre of Excellence for All Sky Astrophysics in Three Dimensions (ASTRO-3D), Australia 3Departments of Astronomy and of Physics, University of California, Berkeley, CA 94720, USA 4Sydney Institute for Astronomy, School of Physics A28, University of Sydney, NSW 2006, Australia 5Miller Professor, Miller Institute, University of California, Berkeley, CA 94720, USA arXiv:1812.01615v2 [astro-ph.GA] 13 Dec 2018 1 Xxxx. Xxx. Xxx. Xxx. 2019. 59:1{76 Keywords This article's doi: star clusters, star formation, globular clusters, open clusters and 10.1146/((please add article doi)) associations, stellar abundances Copyright c 2019 by Annual Reviews. All rights reserved Abstract Star clusters stand at the intersection of much of modern astrophysics: the interstellar medium, gravitational dynamics, stellar evolution, and cosmology. Here we review observations and theoretical models for the formation, evolution, and eventual disruption of star clusters. Current literature suggests a picture of this life cycle with several phases: • Clusters form in hierarchically-structured, accreting molecular clouds that convert gas into stars at a low rate per dynamical time until feedback disperses the gas. • The densest parts of the hierarchy resist gas removal long enough to reach high star formation efficiency, becoming dynamically- relaxed and well-mixed. These remain bound after gas removal. • In the first ∼ 100 Myr after gas removal, clusters disperse mod- erately fast, through a combination of mass loss and tidal shocks by dense molecular structures in the star-forming environment.