The Formation and Early Evolution of Young Massive Clusters

Author(s)

Steven N. Longmore, J. M. Diederik Kruijssen, Nate Bastian, John Bally, Jill Rathborne, Leonardo Testi, Andrea Stolte, James Dale, Eli Bressert, Joao Alves

Abstract

We review the formation and early evolution of the most massive and

dense young stellar clusters, focusing on the role they can play in our

understanding of star and planet formation as a whole. Young massive

cluster (YMC) progenitor clouds in the Galactic Center can accumulate to

a high enough density without forming stars that the initial

protostellar densities are close to the final stellar density. For this

to hold in the disk, the time scale to accumulate the gas to such high

densities must be much shorter than the star formation timescale.

Otherwise the gas begins forming stars while it is being accumulated to

high density. The distinction between the formation regimes in the two

environments is consistent with the predictions of

environmentally-dependent density thresholds for star formation. This

implies that stars in YMCs of similar total mass and radius can have

formed at widely different initial protostellar densities. The fact that

no systematic variations in fundamental properties are observed between

YMCs in the disk and Galactic Center suggests stellar mass assembly is

not strongly affected by the initial protostellar density. We review

recent theoretical advances and summarize the debate on three key open

questions: the initial (proto)stellar distribution, infant (im)mortality

and age spreads within YMCs. We conclude: the initial protostellar

distribution is likely hierarchical; YMCs likely experienced a formation

history that was dominated by gas exhaustion rather than gas expulsion;

YMCs are dynamically stable from a young age; and YMCs have age spreads

much smaller than their mean age. Finally, we show that it is plausible

that metal-rich globular clusters may have formed in a similar way to

YMCs in nearby galaxies. In summary, the study of YMC formation bridges

star/planet formation in the solar neighborhood to the oldest structures

in the local Universe. [abridged]

Organisation(s)

Department of Astrophysics

Publication date

01-2014

Austrian Fields of Science 2012

103004 Astrophysics, 103003 Astronomy

Keywords

Portal url

https://ucrisportal.univie.ac.at/en/publications/the-formation-and-early-evolution-of-young-massive-clusters(99beefed-4dea-4fd6-84d5-2b04f6eec219).html