Milone, AP, Marino, AF, Bedin, LR, Anderson, J, Apai, D, Bellini, A, DIeball, A, Salaris, M, Libralato, M, Nardiello, D, Bergeron, P, Burgasser, AJ, Rees, JM, Rich, RM and Richer, HB (2019) The HST Large Programme on NGC 6752 - II. Multiple populations at the bottom of the main sequence probed in NIR. Monthly Notices of the Royal Astronomical Society, 484 (3). pp. 4046-4053. ISSN 0035-8711

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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⊙. 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⊙). 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⊙. As a consequence, the evidence that the properties of multiple populations do not depend on stellar mass is a constraint for the formation scenarios. © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.

Item Type:	Article
Uncontrolled Keywords:	0201 Astronomical and Space Sciences
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	Oxford University Press
Date Deposited:	25 Mar 2019 13:00
Last Modified:	03 Sep 2021 23:42
DOI or ID number:	10.1093/mnras/stz277
URI:	https://researchonline.ljmu.ac.uk/id/eprint/10394

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