Issue |
A&A
Volume 383, Number 1, FebruaryIII 2002
|
|
---|---|---|
Page(s) | 137 - 152 | |
Section | Galactic structure, stellar clusters, and populations | |
DOI | https://doi.org/10.1051/0004-6361:20011704 | |
Published online | 15 February 2002 |
Dynamical masses of young star clusters in NGC 4038/4039*
Max-Planck-Institut für extraterrestrische Physik Giessenbachstraße, 85748 Garching, Germany e-mail: mlehnert, thatte, genzel@mpe.mpg.de
Corresponding author: S. Mengel, mengel@strw.leidenuniv.nl
Received:
11
September
2001
Accepted:
26
November
2001
In order to estimate the masses of the compact, young star clusters in
the merging galaxy pair, NGC 4038/4039 (“the Antennae”), we have
obtained medium and high resolution spectroscopy using ISAAC on VLT-UT1
and UVES on VLT-UT2 of five such clusters. The velocity dispersions
were estimated using the stellar absorption features of CO at 2.29
μm and metal absorption lines at around 8500 Å, including lines of
the Calcium Triplet. The size scales and light profiles were measured
from HST images. From these data and assuming Virial equilibrium, we
estimated the masses of five clusters. The resulting masses range from
6.5 105 to 4.7
106
. These masses are
large, a factor of a few to more than 10 larger than the typical mass of a
globular cluster in the Milky Way. The mass-to-light ratios for these clusters in
the V- and K-bands in comparison with stellar synthesis models suggest
that to first order the IMF slopes are approximately consistent with
Salpeter for a mass range of 0.1 to 100
. However, the
clusters show a significant range of possible IMF slopes or lower mass
cut-offs and that these variations may correlate with the interstellar
environment of the cluster. Comparison with the results of
Fokker-Planck simulations of compact clusters with properties similar to
the clusters studied here suggest that they are likely to be long-lived
and may lose a substantial fraction of their total mass. This mass loss
would make the star clusters obtain masses which are comparable
to the typical mass of a globular cluster.
Key words: galaxies: star clusters / galaxies: individual: NGC 4038/4039 / IMF / galaxies: clusters: general / stars: fondamental parameters
© ESO, 2002
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