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

Abstract

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.