Multiple stellar populations in three rich Large Magellanic Cloud star clusters

Abstract

We present deep colour-magnitude diagrams for three rich intermediate-age star clusters in the Large Magellanic Cloud, constructed from archival ACS F435W and F814W imaging. All three clusters exhibit clear evidence for peculiar main-sequence turn-offs. NGC 1846 and 1806 each possess two distinct turn-off branches, while the turn-off for NGC 1783 shows a much larger spread in colour than can be explained by the photometric uncertainties. We demonstrate that although all three clusters contain significant populations of unresolved binary stars, these cannot be the underlying cause of the observed turn-off morphologies. The simplest explanation is that each cluster is composed of at least two different stellar populations with very similar metal abundances but ages separated by up to ~300 Myr. The origin of these unusual properties remains unidentified; however, the fact that at least three massive clusters containing multiple stellar populations are now known in the LMC suggests a potentially significant formation channel.

To appear in ApJ Letters, replaced with accepted version

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Cited by in corpus (6)

• A large C+N+O abundance spread in giant stars of the globular cluster NGC 1851
• Discovery of two distinct red clumps in NGC419: a rare snapshot of a cluster at the onset of degeneracy
• Joint Analysis of near-infrared properties and surface brightness fluctuations of LMC star clusters
• On the origin of double main-sequence turn-offs in star clusters of the Magellanic Clouds
• Biases on initial mass function determinations. III. Cluster masses derived from unresolved photometry
• Mass segregation in young star clusters: can it be detected from the integrated photometric properties?