Abundance scaling in stars, nebulae and galaxies

TL;DR

This paper introduces a new physically motivated method for scaling elemental abundances in nebular models based on extensive stellar data, improving upon the traditional uniform scaling approach.

Contribution

It proposes a parametric enrichment factor for abundance scaling, enabling more realistic nebular modeling across various astrophysical environments.

Findings

Developed a new abundance scaling method based on stellar data.

Provided a parametric framework for converting between different abundance scales.

Applicable to diverse astrophysical objects from local HII regions to high-redshift galaxies.

Abstract

We present a new basis for scaling abundances with total metallicity in nebular photoionisation models, based on extensive Milky Way stellar abundance data, to replace the uniform scaling normally used in the analysis of HII regions. Our goal is to provide a single scaling method and local abundance reference standard for use in nebular modelling and its key inputs, the stellar atmosphere and evolutionary track models. We introduce a parametric enrichment factor, zeta, to describe how atomic abundances scale with total abundance, and which allows for a simple conversion between scales based on different reference elements (usually oxygen or iron) . The models and parametric description provide a more physically realistic approach than simple uniform abundance scaling. With appropriate parameters, the methods described here may be applied to HII regions in the Milky Way, large and dwarf galaxies in the local universe, Active Galactic Nuclei (AGNs), and to star forming regions at high redshift.