The origin of stellar populations in the Galactic bulge from chemical abundances

Francesca Matteucci, Valeria Grisoni, Emanuele Spitoni, Anna Zulianello, Alvaro Rojas-Arriagada, Mathias Schultheis, Nils Ryde

The origin of stellar populations in the Galactic bulge from chemical abundances See arXiv version 10 pages, 9 figures, submitted


In this work, we study the formation and chemical evolution of the Galactic bulge with particular focus on the abundance pattern ([Mg/Fe] vs. [Fe/H]), metallicity and age distribution functions. We consider detailed chemical evolution models for the Galactic bulge and inner disc, with the aim of sheding light on the connection between these components and the origin of bulge stars. In particular, we first present a model assuming a fast and intense star formation, with the majority of bulge stars forming on a timescale less than 1 Gyr. Then we analyze the possibility of two distinct stellar populations in the bulge, as suggested by Gaia-ESO and APOGEE data. These two populations, one metal poor and the other metal rich, can have had two different origins: i) the metal rich formed after a stop of \(\sim\) 250 Myr in the star formation rate of the bulge, or ii) the metal rich population is made of stars formed in the inner disc and brought into the bulge by the early secular evolution of the bar. We also examine the case of multiple star bursts in the bulge with consequent formation of multiple populations, as suggested by studies of microlensed stars. After comparing model results and observations, we suggest that the most likely explanation is that there are two main stellar populations, both made mainly by old stars (\(> 10\) Gyr), with the metal rich and younger one formed by inner disc stars, in agreement with kinematic arguments.

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