The Hubble Space Telescope UV Legacy Survey of galactic globular clusters - II. The seven stellar populations of NGC 7089 (M2)⋆

Milone, A. P.; Marino, A. F.; Piotto, G.; Bedin, L. R.; Anderson, J.; Renzini, A.; King, I. R.; Bellini, A.; Brown, T. M.; Cassisi, S.; D'Antona, F.; Jerjen, H.; Nardiello, D.; Salaris, M.; Marel, R. P. van der; Vesperini, E.; Yong, D.; Aparicio, A.; Sarajedini, A.; Zoccali, M.
Bibliographical reference

Monthly Notices of the Royal Astronomical Society, Volume 447, Issue 1, p.927-938

Advertised on:
2
2015
Number of authors
20
IAC number of authors
1
Citations
124
Refereed citations
110
Description
We present high-precision multiband photometry for the globular cluster (GC) M2. We combine the analysis of the photometric data obtained from the Hubble Space Telescope UV Legacy Survey of Galactic GCs GO-13297, with chemical abundances by Yong et al., and compare the photometry with models in order to analyse the multiple stellar sequences we identified in the colour-magnitude diagram. We find three main stellar components, composed of metal-poor, metal-intermediate, and metal-rich stars (hereafter referred to as population A, B, and C, respectively). The components A and B include stars with different s-process element abundances. They host six sub-populations with different light-element abundances, and exhibit an internal variation in helium up to ΔY ˜ 0.07 dex. In contrast with M22, another cluster characterized by the presence of populations with different metallicities, M2 contains a third stellar component, C, which shows neither evidence for sub-populations nor an internal spread in light-elements. Population C does not exhibit the typical photometric signatures that are associated with abundance variations of light elements produced by hydrogen burning at hot temperatures. We compare M2 with other GCs with intrinsic heavy-element variations and conclude that M2 resembles M22, but it includes an additional stellar component that makes it more similar to the central region of the Sagittarius galaxy, which hosts a GC (M54) and the nucleus of the Sagittarius galaxy itself.
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The general aim of the project is to research the structure, evolutionary history and formation of galaxies through the study of their resolved stellar populations, both from photometry and spectroscopy. The group research concentrates in the most nearby objects, namely the Local Group galaxies including the Milky Way and M33 under the hypothesis
Martín
López Corredoira