Star cluster disruption

TL;DR

This review discusses the evolution and survival of star clusters, emphasizing how initial conditions and environment influence their longevity and their use as tracers of galactic star formation history.

Contribution

It provides a theoretical overview of star cluster evolution, highlighting the impact of initial density and environment on their long-term survival.

Findings

Clusters with initial densities >10^4 Msun pc-3 survive gas expulsion.

Clusters with densities around 10^3 Msun pc-3 are stable after 10 Myr.

Lower density clusters disperse within a few tens of Myrs.

Abstract

Star clusters are often used as tracers of major star formation events in external galaxies as they can be studied up to much larger distances than individual stars. It is vital to understand their evolution if they are used to derive, for example, the star formation history of their host galaxy. More specifically, we want to know how cluster lifetimes depend on their environment and structural properties such as mass and radius. This review presents a theoretical overview of the early evolution of star clusters and the consequent long term survival chances. It is suggested that clusters forming with initial densities of >10^4 Msun pc-3 survive the gas expulsion, or "infant mortality", phase. At ~10 Myr they are bound and have densities of 10^{3+/-1} Msun pc-3. After this time they are stable against expansion by stellar evolution, encounters with giant molecular clouds and will most likely survive for another Hubble time if they are in a moderate tidal field. Clusters with lower initial densities (<100 Msun pc-3) will disperse into the field within a few 10s of Myrs. Some discussion is provided on how extra galactic star cluster populations and especially their age distributions can be used to gain insight in disruption.