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arXiv · 1801.09670

Kron 3: a fourth intermediate age cluster in the SMC with evidence of multiple populations

K. Hollyhead·C. Lardo·N. Kacharov·N. Bastian·M. Hilker·M. Rejkuba·A. Koch·E. K. Grebel·I. Georgiev
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Abstract

We present the results of a spectroscopic study of the intermediate age (approximately 6.5 Gyr) massive cluster Kron 3 in the Small Magellanic Cloud. We measure CN and CH band strengths (at 3839 and 4300 Angstroms respectively) using VLT FORS2 spectra of 16 cluster members and find a sub-population of 5 stars enriched in nitrogen. We conclude that this is evidence for multiple populations in Kron 3, the fourth intermediate age cluster, after Lindsay 1, NGC 416 and NGC 339 (ages 6-8 Gyr), to display this phenomenon originally thought to be a unique characteristic of old globular clusters. At 6.5 Gyr this is one of the youngest clusters with multiple populations, indicating that the mechanism responsible for their onset must operate until a redshift of at least 0.75, much later than the peak of globular cluster formation at redshift ~3.

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K. Hollyhead, C. Lardo, N. Kacharov, N. Bastian, M. Hilker, M. Rejkuba, A. Koch, E. K. Grebel, I. Georgiev. 2018-01-29. Kron 3: a fourth intermediate age cluster in the SMC with evidence of multiple populations. https://doi.org/10.1093/mnras/sty230

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