Multiple stellar populations in the globular cluster NGC 1851 (E. Carretta et al.)

Vol. 533
In section 5. Galactic structure, stellar clusters and populations

Multiple stellar populations in the globular cluster NGC 1851

by E. Carretta, S. Lucatello, R.G. Gratton, A. Bragaglia, and V. D'Orazi, A&A 533, A69

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This paper presents the largest sample of high-resolution spectroscopic abundances for a wide range of elements (O, Na, Mg, Al, Si, Ca, Ti, Sc, V, Mn, Co, Ni, Cu, Y, Zr, Ba, La, Ce, Nd, Eu, Dy) for 124 red giant stars in the globular cluster NGC1851 coming from VLT/FLAMES observations. This globular cluster is known to contain multiple stellar populations, and with this wide array of abundances, the authors were able to determine a classification scheme using Fe and Ba, which made a clear separation into metal-rich and metal-poor populations. Both populations have distinct properties, both consistent with genuine globular clusters. There are several possible interpretations of the presence of two distinct populations within NGC1851 with different alpha-element, p- and n- capture element properties. It is possible that this is the result of the past merger of two distinct globular clusters with an age difference of ~1Gyr.