Using Cepheids to determine the galactic abundance gradient. III.First results for the outer disc

TL;DR

This study extends the analysis of galactic metallicity gradients using Cepheids to the outer disc beyond 10 kpc, revealing a potential discontinuity at 10 kpc that informs models of galactic chemical evolution.

Contribution

It provides new high-resolution spectroscopic data for Cepheids in the outer galactic disc, identifying a metallicity discontinuity at 10 kpc, which was previously suggested but not confirmed.

Findings

Indicates a metallicity discontinuity at 10 kpc.

Samples galactic distances from 10 to 12 kpc.

Supports earlier findings of a gradient break.

Abstract

As a continuation of our previous work, which concerned the radial abundance distribution in the galactic disc over the distances 4-10 kpc this paper presents the first results on the metallicicty in the outer disc (RG > 10 kpc). Based on high-resolution spectra obtained for 19 distant Cepheids we sampled galactocentric distances from 10 to 12 kpc. Combined with the results of our previous work on the inner and middle parts of the galactic disc, the present data enable one to study the structure of the radial abundance distribution over a large baseline. In particular, we find indications of a discontinuity in the radial abundance distribution for iron as well as a number of the other elements. The discontinuity is seen at a galactocentric distance RG = 10 kpc. This finding supports the results reported earlier by Twarog et al. (1997).