Published in Annual Review of Astronomy and
Astrophysics, vol. 57, p.227-303, 2019.
https://arxiv.org/abs/1812.01615
STAR CLUSTERS ACROSS COSMIC TIME
Mark R. Krumholz 1,2, Christopher F. McKee 3,
and Joss Bland-Hawthorn 2,4,5
1 Research
School of Astronomy and Astrophysics,
Australian National
University, Canberra, ACT 2611, Australia
2 Centre of
Excellence for All Sky Astrophysics in Three Dimensions (ASTRO-3D),
Australia
3
Departments of
Astronomy and of Physics,
University of
California, Berkeley, CA 94720, USA
4 Sydney Institute for Astronomy,
School of Physics A28,
University of Sydney, NSW 2006, Australia
5 Miller Professor,
Miller
Institute,
University of
California, Berkeley, CA 94720, USA
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 moderately fast, through a combination of
mass loss and tidal shocks by dense molecular structures in the
star-forming environment.
- After ∼ 100 Myr, clusters lose mass via
two-body relaxation and shocks by giant molecular clouds, processes that
preferentially affect low-mass clusters and cause a turnover in the
cluster mass function to appear on ∼ 1−10 Gyr
timescales.
- Even after dispersal, some clusters remain
coherent and thus detectable in chemical or action space for multiple
galactic orbits.
In the next decade a new generation of space- and AO-assisted
ground-based telescopes will enable us to test and refine this picture.
Keywords : star clusters, star formation, globular clusters, open
clusters and associations, stellar abundances
The paper is in pdf format.