Issue |
A&A
Volume 429, Number 1, January I 2005
|
|
---|---|---|
Page(s) | 173 - 179 | |
Section | Galactic structure, stellar clusters, and populations | |
DOI | https://doi.org/10.1051/0004-6361:20041476 | |
Published online | 13 December 2004 |
Disruption time scales of star clusters in different galaxies
1
Astronomical Institute, Utrecht University, Princetonplein 5, 3584CC Utrecht, The Netherlands e-mail: [lamers;gieles]@astro.uu.nl
2
Astronomical Institute, University of Amsterdam, Kruislaan 403, 1098SJ Amsterdam, The Netherlands e-mail: spz@science.uva.nl
3
Informatics Institute, University of Amsterdam, Kruislaan 403, 1098SJ Amsterdam, The Netherlands
Received:
15
June
2004
Accepted:
2
September
2004
The observed average lifetime of the population of star clusters in the
Solar Neighbourhood, the Small Magellanic Cloud and in selected
regions of M 51 and M 33 is compared with simple theoretical predictions and with
the results of N-body simulations.
The empirically derived lifetimes (or disruption times)
of star clusters depend on their initial mass
as tdis in all four galaxies.
N-body simulations have shown that the predicted
disruption time of clusters in a tidal field scales as
tdis, where
trh is the initial half-mass relaxation time and tcr
is the crossing time for a cluster in equilibrium. We show that
this can be approximated accurately by
tdis for
clusters in the mass range of about 103 to 106 , in
excellent agreement with the observations.
Observations of clusters in different extragalactic environments show
that tdis also depends on the ambient density in the galaxies where
the clusters reside. Linear analysis predicts that
the disruption time will depend on the ambient density of the cluster
environment as tdis.
This relation is consistent with N-body simulations. The
empirically derived
disruption times of clusters in the Solar Neighbourhood, in the SMC
and in M 33 agree with these predictions. The best fitting expression
for the disruption time is tdis
where Mcl is the initial mass of the cluster
and
Myr. The disruption times of star
clusters in M 51 within 1-5 kpc from the nucleus, is shorter than predicted
by about an order of magnitude. This
discrepancy might be due to the strong tidal field variations in M 51,
caused by the strong density contrast between the spiral arms and
interarm regions, or to the disruptive forces from giant molecular clouds.
Key words: Galaxy: open clusters and associations: general / galaxies: individual: M 33 / galaxies: individual: M 51 / galaxies: individual: SMC / galaxies: star clusters / Galaxy: globular clusters: general
© ESO, 2005
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