Discovery of a New Stellar Subpopulation Residing in the (Inner) Stellar Halo of the Milky Way

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Fernandez-Trincado, Jose G. ^{[1, 2]} ; Beers, Timothy C. ^{[3, 4]} ; Placco, Vinicius M. ^{[3, 4]} ; Moreno, Edmundo ^[5] ; Alves-Brito, Alan ^[6] ; Minniti, Dante ^{[7, 8, 9]} ; Tang, Baitian ^[10] ; Perez-Villegas, Angeles ^[11] ; Reyle, Celine ^[2] ; Robin, Annie C. ^[2] ; Villanova, Sandro ^[12]

Afiliação do(s) autor(es):Mostrar menos -

^[1] Univ Atacama, Inst Astron & Ciencias Planetarias, Copayapu 485, Copiapo - Chile

^[2] Univ Bourgogne Franche Compte, OSU THETA Franche Compte, Observ Besancon, CNRS UMR 6213, Inst Utinam, BP 1615, F-251010 Besancon - France

^[3] Univ Notre Dame, Dept Phys, Notre Dame, IN 46556 - USA

^[4] Univ Notre Dame, JINA Ctr Evolut Elements, Notre Dame, IN 46556 - USA

^[5] Univ Nacl Autonoma Mexico, Inst Astron, Apdo Postal 70264, Mexico City 04510, DF - Mexico

^[6] Univ Fed Rio Grande do Sul, Inst Fis, Ave Bento Goncalves 9500, Porto Alegre, RS - Brazil

^[7] Vatican Observ, V-00120 Vatican City - Vatican

^[8] Univ Andres Bello, Fac Ciencias Exactas, Dept Fis, Ave Fernandez Concha 700, Santiago - Chile

^[9] Millennium Inst Astrophys, Ave Vicuna Mackenna 4860, Santiago 7820436 - Chile

^[10] Sun Yat Sen Univ, Sch Phys & Astron, Zhuhai 519082 - Peoples R China

^[11] Univ Sao Paulo, IAG, Rua Matao 1226, Cidade Univ, BR-05508900 Sao Paulo, SP - Brazil

^[12] Univ Concepcion, Dept Astron, Casilla 160-C, Concepcion - Chile

• Tipo de documento: Artigo Científico
• Fonte: Astrophysical Journal Letters; v. 886, n. 1 NOV 20 2019.
• Citações Web of Science: 0

Resumo

We report the discovery of a unique collection of metal-poor giant stars that exhibit anomalously high levels of Si-28, clearly above typical Galactic levels. Our sample spans a narrow range of metallicities, peaking at ?1.07;;0.06, and exhibits abundance ratios of {[}Si, Al/Fe] that are as extreme as those observed in Galactic globular clusters (GCs), and Mg is slightly less overabundant. In almost all the sources we used, the elemental abundances were redetermined from high-resolution spectra, which were reanalyzed assuming LTE. Thus, we compiled the main element families, namely, the light elements (C, N), ?-elements (O, Mg, Si), iron-peak element (Fe), s-process elements (Ce, Nd), and the light odd-Z element (Al). We also provide dynamical evidence that most of these stars lie on tight (inner) halo-like and retrograde orbits passing through the bulge. Such kinds of objects have been found in present-day halo GCs, providing the clearest chemical signature of past accretion events in the (inner) stellar halo of the galaxy, possibly formed as the result of dissolved halo GCs. Their chemical composition is, in general, similar to that of typical GC populations, although several differences exist. (AU)

• Processo FAPESP: 17/15893-1 - Órbitas de aglomerados globulares do bojo: formação e evolução da Via Láctea
• Beneficiário: Maria de Los Angeles Perez Villegas
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado