The evolution of two stellar populations in globular clusters I. The dynamical mixing timescale

Decressin, T., Baumgardt, H. and Kroupa, P. (2008) The evolution of two stellar populations in globular clusters I. The dynamical mixing timescale. Astronomy and Astrophysics, 492 1: 101-109. doi:10.1051/0004-6361:200810275

Author Decressin, T.
Baumgardt, H.
Kroupa, P.
Title The evolution of two stellar populations in globular clusters I. The dynamical mixing timescale
Journal name Astronomy and Astrophysics   Check publisher's open access policy
ISSN 0004-6361
Publication date 2008-12
Sub-type Article (original research)
DOI 10.1051/0004-6361:200810275
Open Access Status DOI
Volume 492
Issue 1
Start page 101
End page 109
Total pages 9
Place of publication Les Ulis, France
Publisher E D P Sciences
Language eng
Formatted abstract
Aims. We investigate the long-term dynamical evolution of two distinct stellar populations of low-mass stars in globular clusters in
order to study whether the energy equipartition process can explain the high number of stars harbouring abundance anomalies seen in
globular clusters.
Methods. We analyse N-body models by artificially dividing the low-mass stars (m ≤ 0.9 M) into two populations: a small number
of stars (second generation) consistent with an invariant IMF and with low specific energies initially concentrated towards the cluster centre mimic stars with abundance anomalies. These stars form from the slow winds of fast-rotating massive stars. The main part of
low-mass (first generation) stars has the pristine composition of the cluster. We study in detail how the two populations evolve under
the influence of two-body relaxation and the tidal forces due to the host galaxy.
Results. Stars with low specific energy initially concentrated toward the cluster centre need about two relaxation times to achieve
a complete homogenisation throughout the cluster. For realistic globular clusters, the number ratio between the two populations
increases only by a factor 2.5 due to the preferential evaporation of the population of outlying first generation stars. We also find that
the loss of information on the stellar orbital angular momentum occurs on the same timescale as spatial homogenisation.
Conclusions. To reproduce the high number of chemically anomalous stars in globular clusters by preserving an invariant IMF, more
efficient mechanisms such as primordial gas expulsion are needed to expel the stars in the outer cluster parts on a short timescale.
Keyword Globular clusters: general
Stellar dynamics
Methods: N-body simulations
Self-Enrichment scenario
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Mathematics and Physics
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