Bibcode
Hasselquist, S.; Carlin, Jeffrey L.; Holtzman, Jon A.; Shetrone, Matthew; Hayes, Christian R.; Cunha, Katia; Smith, Verne; Beaton, Rachael L.; Sobeck, Jennifer; Allende Prieto, C.; Majewski, Steven R.; Anguiano, Borja; Bizyaev, Dmitry; García-Hernández, D. A.; Lane, Richard R.; Pan, Kaike; Nidever, David L.; Fernández-Trincado, José. G.; Wilson, John C.; Zamora, O.
Bibliographical reference
The Astrophysical Journal, Volume 872, Issue 1, article id. 58, 14 pp. (2019).
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2019
Journal
Citations
39
Refereed citations
39
Description
The SDSS-IV Apache Point Observatory Galactic Evolution Experiment
(APOGEE) survey provides precise chemical abundances of 18 chemical
elements for ∼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 ∼ 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] ∼ ‑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] ∼
‑0.6, and had a similar star formation history to Sgr before
merging.
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