The HST large programme on omega Centauri - I. Multiple stellar populations at the bottom of the main sequence probed in NIR-Optical
AuthorMilone, A. P.
Marino, A. F.
Bedin, L. R.
Burgasser, A. J.
Rees, J. M.
AffiliationUniv Arizona, Dept Astron
Univ Arizona, Steward Observ
Univ Arizona, Lunar & Planetary Lab
Russell and colour
stars: Population II
globular clusters: general
globular clusters: individual: omega Centauri M4, NGC2808
MetadataShow full item record
PublisherOXFORD UNIV PRESS
CitationThe HST large programme on omega Centauri - I. Multiple stellar populations at the bottom of the main sequence probed in NIR-Optical 2017, 469 (1):800 Monthly Notices of the Royal Astronomical Society
Rights© 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
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AbstractAs part of a large investigation with Hubble Space Telescope to study the faintest stars within the globular cluster omega Centauri, in this work we present early results on the multiplicity of its main sequence (MS) stars, based on deep optical and near-infrared observations. By using appropriate colour-magnitude diagrams, we have identified, for the first time, the two main stellar Populations I and II along the entire MS, from the turn-off towards the hydrogen-burning limit. We have compared the observations with suitable synthetic spectra of MS stars and conclude that the two main sequences (MSs) are consistent with stellar populations with different metallicity, helium and light-element abundance. Specifically, MS-I corresponds to a metal-poor stellar population ([Fe/H] similar to -1.7) with Y similar to 0.25 and [O/Fe] similar to 0.30. The MS-II hosts helium-rich (Y similar to 0.37-0.40) stars with metallicity ranging from [Fe/H] similar to -1.7 to -1.4. Below the MS knee (m(F160W) similar to 19.5), our photometry reveals that each of the two main MSs hosts stellar subpopulations with different oxygen abundances, with very O-poor stars ([O/Fe] similar to -0.5) populating the MS-II. Such a complexity has never been observed in previous studies of M-dwarfs in globular clusters. A few months before the launch of the James Webb Space Telescope, these results demonstrate the power of optical and near-infrared photometry in the study of multiple stellar populations in globular clusters.
VersionFinal published version
SponsorsNASA [NAS 5-26555, GO-14118, GO-14662]; Australian Research Council through Discovery Early Career Researcher Awards [DE150101816, DE160100851]; NASA through a grant from the Space Telescope Science Institute [GO-14118, GO-14662]