Abundance gradients in the galactic disk: space and time variations

TL;DR

This study investigates how chemical abundance gradients in the galactic disk vary across space and time, revealing a flattening trend over the last 6-8 billion years based on diverse astronomical data.

Contribution

It provides new insights into the spatial and temporal evolution of galactic abundance gradients using multiple stellar and nebular objects.

Findings

Gradients tend to flatten at large galactocentric distances.

A steep decrease in abundances is observed near the bulge-disk interface.

Gradients have likely flattened over the last 6-8 billion years.

Abstract

Recent work on abundance gradients have focussed not only on their magnitudes, but also on their spatial and temporal variations. In this work, we analyze the behaviour of radial abundance gradients in the galactic disk giving special emphasis on these variations. The data used includes planetary nebulae and objects in different age brackets, namely open clusters, HII regions, cepheid variables and stars in OB associations. We find evidences for a space variation of the radial gradients as measured for element ratios such as O/H, S/H, Ne/H, Ar/H and [Fe/H], in the sense that the gradients tend to flatten out at large galactocentric distances. Moreover, near the bulge-disk interface a steep decrease in the abundances is observed. The time evolution of the gradients is also evaluated on the basis of approximate ages attributed to the central stars of planetary nebulae and open cluster stars. It is concluded that the available data is consistent with a time flattening of the gradients during the last 6 to 8 Gyr, a time interval in which the age determinations are probably more accurate.