Formation of leaky clusters and OB associations Susanne Pfalzner Max-Planck_institut für Radioastronomie, Bonn, Germany
In this study we investigate possible formation scenarios for the class of massive clusters often referred to as leaky clusters or OB associations. We use the existing observational data and numerical results of embedded cluster properties and assume a clear correlation between cluster density, size, and age exists. It is shown that the density-radius development over time for embedded clusters can be approximated by ρ ≈ 100 ∗ r-1.3 Msun pc-3. The consequences for the star formation process in leaky clusters are discussed and found to favour an inside-out star formation scenario with an initially low, but later accelerated, star formation rate. Alternative scenarios leading to the observed development are discussed and observable differences are pointed out.
Caption: Fig. 3 in related paper. Cluster mass as a function of cluster radius for embedded clusters. The data points are taken from Lada & Lada (2003), and the best fit for aRb gives a = 359 ± 15 and b = 1.71 ± 0.07.
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