Oxygen abundance distribution in Galactic disc

TL;DR

This study analyzes oxygen abundance in the Galactic thin disc using NLTE methods on Cepheid spectra, revealing a negative radial gradient that may flatten in the outer disc, with implications for Galactic chemical evolution.

Contribution

It provides the first combined NLTE analysis of Cepheid spectra from two telescopes to map oxygen distribution in the Galactic disc.

Findings

Radial (O/H) gradient slope is -0.058 dex/kpc.

Potential flattening of oxygen distribution in outer disc.

Supports previous findings from open clusters and nebulae studies.

Abstract

We have performed a NLTE analysis of the infrared oxygen triplet for a large number of cepheid spectra obtained with the Hobby-Eberly telescope. These data were combined with our previous NLTE results for the stars observed with Max Planck Gesellschaft telescope with the aim to investigate oxygen abundance distribution in Galactic thin disc. We find the slope of the radial (O/H) gradient value to be equal -0.058 dex/kpc. Nevertheless, we found that there could be a hint that the distribution might become flatter in the outer parts of the disc. This is also supported by other authors who studied open clusters, planetary nebulae and H II regions. Some mechanisms of flattening are discussed.