Triangulum–Andromeda Overdensity: a Region with a Complex Stellar Population
AuthorSales Silva, J. V.
Perottoni, H. D.
Rocha-Pinto, H. J.
Majewski, S. R.
AffiliationUniv Arizona, Steward Observ
MetadataShow full item record
PublisherIOP PUBLISHING LTD
CitationJ. V. Sales Silva et al 2019 ApJ 886 113
RightsCopyright © 2019. The American Astronomical Society. All rights reserved.
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at firstname.lastname@example.org.
AbstractThe 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.
VersionFinal published version
SponsorsFAPERJCarlos Chagas Filho Foundation for Research Support of the State of Rio de Janeiro (FAPERJ) [202.756/2016]; Brazilian Agency CAPESCAPES; FAPESPFundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) [2018/21250-9]