Received on July 19 2005
Star Cluster Survival in Star Cluster Complexes under Extreme Residual Gas Expulsion
|Authors||Fellhauer, M., Kroupa, P.|
|Affiliation||Sternwarte Uni Bonn|
|Accepted by||Astrophysical Journal|
After the stars of a new, embedded star cluster have formed they blow the remaining gas out of the cluster.
Especially winds of massive stars and definitely the on-set of the first supernovae can remove the residual gas from a cluster.
This leads to a very violent mass-loss and leaves the cluster out of dynamical equilibrium. Standard models predict that within
the cluster volume the star formation efficiency (SFE) has to be about 33 per cent for sudden (within one crossing-time of
the cluster) gas expulsion to retain some of the stars in a bound cluster. If the efficiency is lower the stars of the cluster
Recent observations reveal that in strong star bursts star clusters do not form in isolation but in complexes containing dozens
and up to several hundred star clusters, i.e. in super-clusters. By carrying out numerical experiments for such objects placed at
distances > 10 kpc from the centre of the galaxy we demonstrate that under these conditions (i.e. the deeper potential of the
star cluster complex and the merging process of the star clusters within these super-clusters) the SFEs can be as low as 20 per
cent and still leave a gravitationally bound stellar population. Such an object resembles the outer Milky Way globular clusters
and the faint fuzzy star clusters recently discovered in NGC 1023.