The mass function and dynamical mass of young star clusters: why their initial crossing-time matters crucially

Parmentier, Genevieve and Baumgardt, Holger (2012) The mass function and dynamical mass of young star clusters: why their initial crossing-time matters crucially. Monthly Notices of the Royal Astronomical Society, 427 3: 1940-1952. doi:10.1111/j.1365-2966.2012.22004.x

Author Parmentier, Genevieve
Baumgardt, Holger
Title The mass function and dynamical mass of young star clusters: why their initial crossing-time matters crucially
Journal name Monthly Notices of the Royal Astronomical Society   Check publisher's open access policy
ISSN 0035-8711
Publication date 2012-12
Sub-type Article (original research)
DOI 10.1111/j.1365-2966.2012.22004.x
Open Access Status DOI
Volume 427
Issue 3
Start page 1940
End page 1952
Total pages 13
Place of publication Oxford, United Kingdom
Publisher Oxford University Press
Collection year 2013
Language eng
Abstract We highlight the impact of cluster-mass-dependent evolutionary rates upon the evolution of the cluster mass function during violent relaxation, that is, while clusters dynamically respond to the expulsion of their residual star-forming gas. Mass-dependent evolutionary rates arise when the mean volume density of cluster-forming regions is mass-dependent. In that case, even if the initial conditions are such that the cluster mass function at the end of violent relaxation has the same shape as the embedded-cluster mass function (i.e. infant weight-loss is mass-independent), the shape of the cluster mass function does change transiently during violent relaxation. In contrast, for cluster-forming regions of constant mean volume density, the cluster mass function shape is preserved all through violent relaxation since all clusters then evolve at the same mass-independent rate. On the scale of individual clusters, we model the evolution of the ratio of the dynamical mass to luminous mass of a cluster after gas expulsion. Specifically, we map the radial dependence of the time-scale for a star cluster to return to equilibrium. We stress that fields of view a few pc in size only, typical of compact clusters with rapid evolutionary rates, are likely to reveal cluster regions which have returned to equilibrium even if the cluster experienced a major gas expulsion episode a few Myr earlier. We provide models with the aperture and time expressed in units of the initial half-mass radius and initial crossing-time, respectively, so that our results can be applied to clusters with initial densities, sizes, and apertures different from ours.
Keyword Stars: formation
Stars: kinematics and dynamics
ISM: clouds
Galaxies: star clusters: general
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Mathematics and Physics
Official 2013 Collection
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Citation counts: TR Web of Science Citation Count  Cited 6 times in Thomson Reuters Web of Science Article | Citations
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