# Metallicity gradients in M31, M33, NGC 300 and the Milky Way using abundances of different elements

## TL;DR

This study compares metallicity gradients from planetary nebulae and HII regions across four galaxies, revealing flatter gradients in PNe and potential evolution of gradients over time, influenced by stellar migration.

## Contribution

It provides a comparative analysis of metallicity gradients from different element abundances in multiple galaxies, highlighting the evolution of these gradients with stellar population age.

## Key findings

- PN metallicity gradients are flatter than HII regions in all galaxies.
- M31's PN abundances show no relation to galactocentric distance.
- Type I PNe have steeper gradients, similar to HII regions, suggesting gradient steepening over time.

## Abstract

Metallicity gradients derived from planetary nebulae (PNe) using O, Ne, and Ar abundances are studied and compared to those from HII regions in the galaxies M31, M33, NGC 300 and the Milky Way. Galactocentric radii and chemical abundances were collected from the literature, carefully selecting a homogeneous sample for each galaxy. Metallicity gradients shown by PNe are flatter than those of HII regions in all cases. The extreme case is M31 where PN abundances are not related to galactocentric distances and the gradients are consistent with zero. To analyze the evolution of gradients with time we build gradients for Peimbert Type I and non-Type I PNe finding that Type I PNe show steeper gradients than non-Type I PNe and more similar to the ones of HII regions indicating that the chemical gradients might steepen with time. Alternatively, the flat gradients for old PNe show that radial migration could have an important role in the evolution of galaxies.