The multi-zone chemical evolution of the Galactic bulge: predicting abundances for different radial zones

• Main Authors: Cavichia, Oscar, Mollá, Mercedes, Bazán, Juanjo J
• Format: Journal Article
• Language: English
• Published: 13-01-2023
• Subjects: Physics - Astrophysics of Galaxies; Physics - Cosmology and Nongalactic Astrophysics
• DOI: 10.48550/arxiv.2301.05737

Due to its proximity, the stellar populations of the Galactic bulge (GB) can
be resolved and can be studied in detail. This allows tracing the bulge
metallicity distribution function (MDF) for different spatial regions within
the bulge, which may give us clues about the bulge formation and evolution
scenarios. In this work, we developed a chemical evolution model (CEM), taking
into account the mass distribution in the bulge and disc, to derive the radial
dependence of this time-scale in the Galaxy. Since the infall rate depends on
that time scale in the CEM, the results of the model were used to test a
scenario where the bulge is formed inside-out. The obtained results for the
$[\alpha/\mbox{Fe}]$ vs. [Fe/H] relationship, the MDF and the [Fe/H] radial
gradient in the bulge have been compared to available data in the literature.
The model is able to reproduce most of the observational data: the spread in
the relation $[\alpha/\mbox{Fe}]$ vs. [Fe/H], the MDF shape in different
regions of the bulge, the [Fe/H] radial gradient inside it and the
age-metallicity relation, as well as the [$\alpha$/Fe] evolution with age. The
results of the model point to a scenario where the bulk of the bulge stars
pre-existed the boxy/peanut X-shape bar formation. As a result, the classical
origin of the GB is not ruled out and this scenario may be invoked to explain
the chemical properties of the Galactic bulge.