The data reductions applied to the sample of 21 galaxies presented in Paper I have been extensively discussed, in particular the algorithm ishape which is a useful tool for the analysis of compact objects. Tests show that ishape is able to recognise extended objects with good confidence, down to a FWHM of about 1/10 of the FWHM of the PSF itself.
Completeness tests of the cluster samples of the 6 most cluster-rich galaxies were carried out using mksynth, and it was demonstrated that the completeness depends strongly on the extent of the objects.
Using ishape, effective radii of YMCs were obtained, and the distributions in NGC 1313 and NGC 5236 were studied in more detail. We found effective radii of the YMCs in these two galaxies in the range 0-20 pc, in good agreement with results obtained for YMCs in other galaxies, and also similar to those of old globular clusters in the Milky Way and YMCs in the LMC. Some of the objects with U-B<-0.4 may be loosely bound associations, while objects with U-B>-0.4 (older than Myr) are orders of magnitude older than their crossing times, and we may thus conclude that they are genuine clusters. Many of them are significantly more massive than any open cluster in the Milky Way, and may well evolve into objects resembling the old globular clusters seen in the halo of the Milky Way and other galaxies today.Acknowledgements
This research was supported by the Danish Natural Science Research Council through its Centre for Ground-Based Observational Astronomy. The valuable comments of the referee, Dr. Jon Holtzman, which helped improve this paper are appreciated. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
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