Fernández-Alvar, E.; Carigi, Leticia; Schuster, William J.; Hayes, Christian R.; Ávila-Vergara, Nancy; Majewski, Steve R.; Allende Prieto, C.; Beers, Timothy C.; Sánchez, Sebastián F.; Zamora, O.; García-Hernández, D. A.; Tang, Baitian; Fernández-Trincado, José G.; Tissera, Patricia; Geisler, Douglas; Villanova, Sandro
Bibliographical reference
The Astrophysical Journal, Volume 852, Issue 1, article id. 50, 12 pp. (2018).
Description
The formation processes that led to the current Galactic stellar halo
are still under debate. Previous studies have provided evidence for
different stellar populations in terms of elemental abundances and
kinematics, pointing to different chemical and star formation histories
(SFHs). In the present work, we explore, over a broader range in
metallicity (-2.2< [{Fe}/{{H}}]< +0.5), the two stellar
populations detected in the first paper of this series from metal-poor
stars in DR13 of the Apache Point Observatory Galactic Evolution
Experiment (APOGEE). We aim to infer signatures of the initial mass
function (IMF) and the SFH from the two α-to-iron versus iron
abundance chemical trends for the most APOGEE-reliable α-elements
(O, Mg, Si, and Ca). Using simple chemical-evolution models, we infer
the upper mass limit (M up) for the IMF and the star
formation rate, and its duration for each population. Compared with the
low-α population, we obtain a more intense and longer-lived SFH,
and a top-heavier IMF for the high-α population.
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