Astron. Astrophys. Suppl. Ser. 139, 393-415

Young massive star clusters in nearby galaxies

II. Software tools, data reductions and cluster sizes

S.S. Larsen

Copenhagen University Astronomical Observatory, Juliane Maries Vej 32, 2100 Copenhagen Ø, Denmark
e-mail: soeren@astro.ku.dk

Received March 9; accepted July 5, 1999

Abstract:

A detailed description is given of the data analysis leading to the discovery of young massive star clusters (YMCs) in a sample of 21 nearby galaxies. A new useful tool, ishape, for the derivation of intrinsic shape parameters of compact objects is presented, and some test results are shown. Completeness tests for the cluster samples are discussed, and ishape is used to estimate cluster sizes. Half-light radii of 0-20 pc are derived for clusters in 2 of the most cluster-rich galaxies, NGC 1313 and NGC 5236, which is within the range spanned by globular clusters in the Milky Way and by YMCs in the LMC and some starburst galaxies. Photometric data for all clusters, along with positions and estimated half-light radii, are tabulated.

Key words: photometry -- spiral -- star clusters -- techniques: image processing