Triangulum?Andromeda Overdensity: a Region with a Complex Stellar Population

Autor(es)

Sales Silva, J. V. ^[1] ; Perottoni, H. D. ^{[2, 3]} ; Cunha, K. ^{[4, 1]} ; Rocha-Pinto, H. J. ^[2] ; Almeida-Fernandes, F. ^{[2, 3]} ; Souto, Diogo ^{[1, 5]} ; Majewski, S. R. ^[6]

Afiliação do(s) autor(es)

^[1] Observ Nacl MCTIC, R Gen Jose Cristino, 77, BR-20921400 Rio De Janeiro - Brazil

^[2] Univ Fed Rio de Janeiro, Observ Valongo, Lad Pedro Antonio 43, BR-20080090 Rio De Janeiro - Brazil

^[3] Univ Sao Paulo, IAG, Dept Astron, Rua Matao, 1226, BR-05509900 Sao Paulo - Brazil

^[4] Univ Arizona, Steward Observ, Tucson, AZ 85719 - USA

^[5] Univ Fed Sergipe, Dept Fis, Ave Marechal Rondon, S-N, BR-49000000 Sao Cristovao, SE - Brazil

^[6] Univ Virginia, Dept Astron, Charlottesville, VA 22904 - USA

• Tipo de documento: Artigo Científico
• Fonte: ASTROPHYSICAL JOURNAL; v. 886, n. 2 DEC 1 2019.
• Citações Web of Science: 0

Resumo

The Triangulum?Andromeda (TriAnd) overdensity is a distant structure of the Milky Way located in the second Galactic quadrant well below the Galactic plane. Since its discovery, its nature has been under discussion, whether it could be old perturbations of the Galactic disk or the remains of a disrupted former dwarf galaxy. In this study, we investigate the kinematics and chemical composition in 13 stars selected as TriAnd candidates from Two Micron All Sky Survey photometry. The sample was observed using the GRACES high-resolution spectrograph attached to the Gemini North telescope. Based on radial velocities obtained from the spectra and the astrometric data from Gaia, three different kinematic criteria were used to classify our sample stars as belonging to the TriAnd overdensity. The TriAnd confirmed members in our sample span a range in metallicities, including two metal-poor stars ({[}Fe/H];?;?1.3 dex). We show that the adopted kinematical classification also chemically segregates TriAnd and non-TriAnd members of our sample, indicating a unique chemical pattern of the TriAnd stars. Our results indicate different chemical patterns for the {[}Na/Fe], {[}Al/Fe], {[}Ba/Fe], and {[}Eu/Fe] ratios in the TriAnd stars when compared to the chemical pattern of the local disk; the paucity of studies chemically characterizing the outer disk population of the Milky Way is the main obstacle in establishing that the TriAnd population is chemically similar to field stars in the outer disk. But the TriAnd chemical pattern is reminiscent of that found in outer disk open clusters, although the latter are significantly more metal-rich than TriAnd. (AU)

• Processo FAPESP: 18/21250-9 - Identificação de estrelas brilhantes pobres em metais a partir de fotometria Multi-Banda e acompanhamento espectroscópico
• Beneficiário: Hélio Dotto Perottoni
• Linha de fomento: Bolsas no Brasil - Pós-Doutorado