Abundance Patterns in Stars in the Bulge and Galactic Center

TL;DR

This study compares oxygen and iron abundance patterns in stars from the Galactic bulge and center, revealing rapid chemical enrichment in the bulge and similar alpha-element enhancements in the Galactic Center's young stars.

Contribution

It provides new insights into the chemical evolution of the Galactic bulge and center, highlighting differences from the disk and suggesting a rapid enrichment process.

Findings

Bulge stars have elevated [O/Fe] ratios compared to the disk.

Galactic Center stars show nearly uniform, slightly elevated iron abundance.

Young Galactic Center stars exhibit alpha-element enhancements similar to bulge stars.

Abstract

We discuss oxygen and iron abundance patterns in K and M red-giant members of the Galactic bulge and in the young and massive M-type stars inhabiting the very center of the Milky Way. The abundance results from the different bulge studies in the literature, both in the optical and the infrared, indicate that the [O/Fe]-[Fe/H] relation in the bulge does not follow the disk relation, with [O/Fe] values falling above those of the disk. Based on these elevated values of [O/Fe] extending to large Fe abundances, it is suggested that the bulge underwent a rapid chemical enrichment with perhaps a top-heavy initial mass function. The Galactic Center stars reveal a nearly uniform and slightly elevated (relative to solar) iron abundance for a studied sample which is composed of 10 red giants and supergiants. Perhaps of more significance is the fact that the young Galactic Center M-type stars show abundance patterns that are reminiscent of those observed for the bulge population and contain enhanced abundance ratios of alpha-elements relative to either the Sun or Milky Way disk at near-solar metallicities.