# What do planetary nebulae and H II regions reveal about the chemical evolution of nearby dwarf galaxies?

## TL;DR

This paper reviews how planetary nebulae and H II regions serve as key tracers for understanding the chemical evolution and mass-metallicity relation of nearby dwarf galaxies in the Local Group.

## Contribution

It highlights the use of PNe and H II regions as complementary tools for tracing chemical evolution across different galaxy ages.

## Key findings

- PNe provide insights into old and intermediate-age stellar populations.
- H II regions reveal the current chemical composition of galaxies.
- Both tracers help constrain chemical evolution models and the mass-metallicity relation.

## Abstract

The Local Group contains a great number of dwarf irregulars and spheroidals, for which the spectroscopy of individual stars can be obtained. Thus, the chemical evolution of these galaxies can be traced, with the only need of finding populations spanning a large age range and such that we can accurately derive the composition. Planetary nebulae (PNe) are old- and intermediate-age star remnants and their chemical abundances can be obtained up to 3-4 Mpc. H II regions, which are brighter and much easily detected, represent galaxies young content. PNe and H II regions share similar spectroscopic features and are analysed in the same way. Both are among the best tracers of the chemical evolution allowing to draw the chemical time line of nearby galaxies. The focus in this review are the PN and H II region populations as constraints to the chemical evolution models and the mass-metallicity relation of the local universe.