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2010ApJ...713.1343C - Astrophys. J., 713, 1343-1349 (2010/April-3)

A comparison of methods for determining the age distribution of star clusters: application to the Large Magellanic Cloud.


Abstract (from CDS):

The age distribution of star clusters in nearby galaxies plays a crucial role in evaluating the lifetimes and disruption mechanisms of the clusters. Two very different results have been recently found for the age distribution χ(τ) of clusters in the Large Magellanic Cloud (LMC). We found that χ(τ) can be approximately described by a power law χ(τ) {vprop} τγ, with γ ≈ -0.8, by counting clusters in the mass-age plane, i.e., by constructing χ(τ) directly from mass-limited samples. Gieles & Bastian inferred a value of γ ≈ 0, based on the slope of the relation between the maximum mass of clusters in equal intervals of log τ, hereafter, the Mmaxmethod, an indirect technique that requires additional assumptions about the upper end of the mass function. However, our own analysis shows that the Mmax method gives a result consistent with our direct counting method for clusters in the LMC, namely, χ(τ) {vprop} τ–0.8 for τ ≲ 109 yr. The reason for the apparent discrepancy is that our analysis includes many intermediate and high-mass clusters (M > 1.5x103 M), which formed recently (τ ≲ 107 yr), and which are known to exist in the LMC, whereas Gieles & Bastian are missing such clusters. We compile recent results from the literature showing that the age distribution of young star clusters in more than a dozen galaxies, including dwarf and giant galaxies, isolated and interacting galaxies, and irregular and spiral galaxies, has a similar declining shape. We interpret this approximately "universal" shape as primarily due to the progressive disruption of star clusters over their first ∼fewx108 yr, starting soon after formation, and discuss some observational and physical implications of this early disruption for stellar populations in galaxies.

Abstract Copyright:

Journal keyword(s): galaxies: individual: Large Magellanic Cloud - galaxies: star clusters: general - stars: formation

Simbad objects: 21

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