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(Referência obtida automaticamente do Web of Science, por meio da informação sobre o financiamento pela FAPESP e o número do processo correspondente, incluída na publicação pelos autores.)

CNO and F abundances in the globular cluster M22 (NGC 6656)

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Autor(es):
Alves-Brito, A. [1, 2] ; Yong, D. [2] ; Melendez, J. [3] ; Vasquez, S. [1] ; Karakas, A. I. [2]
Número total de Autores: 5
Afiliação do(s) autor(es):
[1] Pontificia Univ Catolica Chile, Dept Astron & Astrofis, Santiago 7820436 - Chile
[2] Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611 - Australia
[3] Univ Sao Paulo, Dept Astron, IAG, BR-05508900 Sao Paulo - Brazil
Número total de Afiliações: 3
Tipo de documento: Artigo Científico
Fonte: Astronomy & Astrophysics; v. 540, APR 2012.
Citações Web of Science: 32
Resumo

Context. Recent studies have confirmed the long standing suspicion that M 22 shares a metallicity spread and complex chemical enrichment history similar to that observed in omega Cen. M 22 is among the most massive Galactic globular clusters and its color-magnitude diagram and chemical abundances reveal the existence of sub-populations. Aims. To further constrain the chemical diversity of M 22, necessary to interpret its nucleosynthetic history, we seek to measure relative abundance ratios of key elements (carbon, nitrogen, oxygen, and fluorine) best studied, or only available, using high-resolution spectra at infrared wavelengths. Methods. High-resolution (R = 50 000) and high S/N infrared spectra were acquired of nine red giant stars with Phoenix at the Gemini-South telescope. Chemical abundances were calculated through a standard 1D local thermodynamic equilibrium analysis using Kurucz model atmospheres. Results. We derive {[}Fe/H] = -1.87 to -1.44, confirming at infrared wavelengths that M 22 does present a {[}Fe/H] spread. We also find large C and N abundance spreads, which confirm previous results in the literature but based on a smaller sample. Our results show a spread in A(C+N+O) of similar to 0.7 dex. Similar to mono-metallic globular clusters, M 22 presents a strong {[}Na/Fe]-{[}O/Fe] anticorrelation as derived from Na and CO lines in the K band. For the first time we recover F abundances in M 22 and find that it exhibits a 0.6 dex variation. We find tentative evidence for a flatter A(F)-A(O) relation compared to higher metallicity globular clusters. Conclusions. Our study confirms and expands upon the chemical diversity seen in this complex stellar system. All elements studied to date show large abundance spreads which require contributions from both massive and low mass stars. (AU)

Processo FAPESP: 10/50930-6 - Evolução química e populações estelares galácticas e extragalácticas, por espectroscopia e imageamento
Beneficiário:Beatriz Leonor Silveira Barbuy
Linha de fomento: Auxílio à Pesquisa - Temático