The MAGIC project. III. Radial and azimuthal Galactic abundance gradients using classical Cepheids

TL;DR

This study investigates chemical abundance gradients and azimuthal variations in the Milky Way using high-resolution spectra of 105 Cepheids, revealing notable azimuthal asymmetries in oxygen abundance that inform galaxy evolution models.

Contribution

It provides detailed chemical compositions of Cepheids and demonstrates the presence of significant azimuthal abundance variations in the Milky Way, supporting recent chemo-dynamical models.

Findings

Negative radial abundance gradients confirmed.

Noticeable azimuthal [O/H] asymmetries of up to 0.2 dex found.

Milky Way shows unique azimuthal abundance variations among spirals.

Abstract

Radial abundance gradients provide sound constraints for chemo-dynamical models of galaxies. Azimuthal variations of abundance ratios are solid diagnostics to understand their chemical enrichment. In this paper we investigate azimuthal variations of abundances in the Milky Way using Cepheids. We provide the detailed chemical composition (25 elements) of 105 Classical Cepheids from high-resolution SALT spectra observed by the MAGIC project. Negative abundance gradients, with abundances decreasing from the inner to the outer disc, have been reported both in the Milky Way and in external galaxies, and our results are in full agreement with literature results. We find azimuthal variations of the oxygen abundance [O/H]. While a large number of external spirals show negligible azimuthal variations, the Milky Way seems to be one of the few galaxies with noticeable [O/H] azimuthal asymmetries. They reach ~0.2 dex in the inner Galaxy and in the outer disc, where they are the largest, thus supporting similar findings for nearby spiral galaxies as well as recent 2D chemo-dynamical models.