PNe as observational constraints in chemical evolution models for NGC 6822

TL;DR

This paper develops chemical evolution models for NGC 6822 using planetary nebulae and H II region abundances to constrain galaxy formation processes and differentiate between abundance determination methods.

Contribution

It introduces models that incorporate observational data from PNe and H II regions, and compares CELs and RLs for abundance measurements to improve understanding of chemical evolution.

Findings

Models can reproduce observed gas mass and O/H with varying outflow and IMF parameters.

Using PNe and H II regions as constraints enhances model robustness.

Discriminates between CELs and RLs abundance determination procedures.

Abstract

Chemical evolution models are useful for understanding the formation and evolution of stars and galaxies. Model predictions will be more robust as more observational constraints are used. We present chemical evolution models for the dwarf irregular galaxy NGC 6822 using chemical abundances of old and young Planetary Nebulae (PNe) and \ion{H}{ii} regions as observational constraints. Two sets of chemical abundances, one derived from collisionally excited lines (CELs) and one, from recombination lines (RLs), are used. We try to use our models as a tool to discriminate between both procedures for abundance determinations. In our chemical evolution code, the chemical contribution of low and intermediate mass stars is time delayed, while for the massive stars the chemical contribution follows the instantaneous recycling approximation. Our models have two main free parameters: the mass-loss rate of a well-mixed outflow and the upper mass limit, $M_{up}$, of the initial mass function (IMF). To reproduce the gaseous mass and the present-day O/H value we need to vary the outflow rate and the $M_{up}$ value.