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NGC6362: the least massive globular cluster with chemically distinct multiple populations

Mucciarelli, A and Dalessandro, E and Massari, D and Bellazzini, M and Ferraro, FR and Lanzoni, B and Lardo, C and Salaris, M and Cassisi, S (2016) NGC6362: the least massive globular cluster with chemically distinct multiple populations. The Astrophysical Journal, 824 (2). ISSN 1538-4357

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Abstract

We present the first measure of Fe and Na abundances in NGC 6362, a low-mass globular cluster where first and second generation stars are fully spatially mixed. A total of 160 member stars (along the red giant branch and the red horizontal branch) have been observed with the multi-object spectrograph FLAMES at the Very Large Telescope. We find that the cluster has an iron abundance of [Fe/H]=--1.09$\pm$0.01 dex, without evidence of intrinsic dispersion. On the other hand, the [Na/Fe] distribution turns out to be intrinsically broad and bimodal. The Na-poor and Na-rich stars populate, respectively, the bluest and the reddest red giant branches detected in the color-magnitude diagrams including the U filter. The red giant branch is composed of a mixture of first and second generation stars in a similar proportion, while almost all the red horizontal branch stars belong to the first cluster generation. Until now, NGC 6362 is the least massive globular cluster where both the photometric and spectroscopic signatures of multiple populations have been detected.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical And Space Sciences, 0305 Organic Chemistry, 0306 Physical Chemistry (Incl. Structural)
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Publisher: American Astronomical Society
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Date Deposited: 28 Jul 2016 11:04
Last Modified: 28 Jul 2016 11:04
DOI or Identification number: 10.3847/0004-637X/824/2/73
URI: http://researchonline.ljmu.ac.uk/id/eprint/3959

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