TY - JOUR
T1 - The HST large programme on Centauri I. Multiple stellar populations at the bottom of the main sequence probed in NIR Optical
AU - Milone, A. P.
AU - Marino, A. F.
AU - Bedin, L. R.
AU - Anderson, J.
AU - Apai, D.
AU - Apai, D.
AU - Bellini, A.
AU - Dotter, A.
AU - Rees, J. M.
N1 - Publisher Copyright:
© 2017 The Authors.
PY - 2017/7/1
Y1 - 2017/7/1
N2 - As part of a large investigation with Hubble Space Telescope to study the faintest stars within the globular cluster ? 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 hydrogenburning 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] ∼ -1.7) with Y ∼ 0.25 and [O/Fe] ∼ 0.30. The MS-II hosts helium-rich (Y ∼ 0.37 0.40) stars with metallicity ranging from [Fe/H] ∼ -1.7 to -1.4. Below the MS knee (mF160W ∼ 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] ∼ -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.
AB - As part of a large investigation with Hubble Space Telescope to study the faintest stars within the globular cluster ? 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 hydrogenburning 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] ∼ -1.7) with Y ∼ 0.25 and [O/Fe] ∼ 0.30. The MS-II hosts helium-rich (Y ∼ 0.37 0.40) stars with metallicity ranging from [Fe/H] ∼ -1.7 to -1.4. Below the MS knee (mF160W ∼ 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] ∼ -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.
KW - Globular clusters: general
KW - Globular clusters: individual: Centauri, M4, NGC2808
KW - Hertzsprung Russell and colour magnitude diagrams
KW - Stars: Population II
KW - Stars: low-mass
UR - http://www.scopus.com/inward/record.url?scp=85027402732&partnerID=8YFLogxK
U2 - 10.1093/mnras/stx836
DO - 10.1093/mnras/stx836
M3 - Article
SN - 0035-8711
VL - 469
SP - 800
EP - 812
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 1
ER -