Identifying Sagittarius Stream Stars by Their APOGEE Chemical Abundance Signatures
Sten Hasselquist, Jeffrey L. Carlin, Jon A. Holtzman, Matthew Shetrone, Christian R. Hayes, Katia Cunha, Verne Smith, Rachael L. Beaton, Jennifer Sobeck, Carlos Allende Prieto, Steven R. Majewski, Borja Anguiano, Dmitry Bizyaev, D. A. Garcia-Hernandez, Richard R. Lane, Kaike Pan, David L. Nidever, Jose. G. Fernandez-Trincado, John C. Wilson, Olga Zamora
The SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey provides precise chemical abundances of 18 chemical elements for similar to 176,000 red giant stars distributed over much of the Milky Way Galaxy (MW), and includes observations of the core of the Sagittarius dwarf spheroidal galaxy (Sgr). The APOGEE chemical abundance patterns of Sgr have revealed that it is chemically distinct from the MW in most chemical elements. We employ a k-means clustering algorithm to six-dimensional chemical space defined by [(C+N)/Fe], [O/Fe], [Mg/Fe], [Al/Fe], [Mn/Fe], and [Ni/Fe] to identify 62 MW stars in the APOGEE sample that have Sgr-like chemical abundances. Of the 62 stars, 35 have Gaia kinematics and positions consistent with those predicted by N-body simulations of the Sgr stream, and are likely stars that have been stripped from Sgr during the last two pericenter passages (<2 Gyr ago). Another 20 of the 62 stars exhibit chemical abundances indistinguishable from the Sgr stream stars, but are on highly eccentric orbits with median r(apo) similar to 25 kpc. These stars are likely the "accreted" halo population thought to be the result of a separate merger with the MW 8-11 Gyr ago. We also find one hypervelocity star candidate. We conclude that Sgr was enriched to [Fe/H] similar to -0.2 before its most recent pericenter passage. If the "accreted halo" population is from one major accretion event, then this progenitor galaxy was enriched to at least [Fe/H] similar to -0.6, and had a similar star formation history to Sgr before merging.
How is this information collected?
This collection of Montana State authored publications is collected by the Library to highlight the achievements of Montana State researchers and more fully understand the research output of the University. They use a number of resources to pull together as complete a list as possible and understand that there may be publications that are missed. If you note the omission of a current publication or want to know more about the collection and display of this information email Leila Sterman.