The HST Large Programme on NGC 6752 - II. Multiple populations at the bottom of the main sequence probed in NIR
Date Issued
2019
Author(s)
Milone, A. P.
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•
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Anderson, J.
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Apai, D.
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Bellini, A.
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Dieball, A.
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Salaris, M.
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Libralato, M.
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Nardiello, D.
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Bergeron, P.
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Burgasser, A. J.
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Rees, J. M.
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Rich, R. M.
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Richer, H. B.
Abstract
Historically, multiple populations in globular clusters (GCs) have been mostly studied from ultraviolet and optical filters down to stars that are more massive than ∼0.6 M_{\odot }. Here, we exploit deep near-infrared (NIR) photometry from the Hubble Space Telescope to investigate multiple populations among M-dwarfs in the GC NGC 6752. We discovered that the three main populations (A, B, and C), previously observed in the brightest part of the colour-magnitude diagram (CMD), define three distinct sequences that run from the main-sequence (MS) knee towards the bottom of the MS (∼0.15 {M}_{\odot }). These results, together with similar findings on NGC 2808, M 4, and ω Centauri, demonstrate that multiple sequences of M-dwarfs are common features of the CMDs of GCs. The three sequences of low-mass stars in NGC 6752 are consistent with stellar populations with different oxygen abundances. The range of [O/Fe] needed to reproduce the NIR CMD of NGC 6752 is similar to the oxygen spread inferred from high-resolution spectroscopy of red giant branch (RGB) stars. The relative numbers of stars in the three populations of M-dwarfs are similar to those derived among RGB and MS stars more massive than ∼0.6 M_{\odot }. As a consequence, the evidence that the properties of multiple populations do not depend on stellar mass is a constraint for the formation scenarios.
Volume
484
Issue
3
Start page
4046
Issn Identifier
0035-8711
Ads BibCode
2019MNRAS.484.4046M
Rights
open.access
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