Star Formation in HII Galaxies. Properties of the ionized gas

TL;DR

This paper introduces a new methodology for analyzing the physical properties of ionized gas in HII galaxies, emphasizing empirical relations and accurate elemental abundance determinations using advanced observational data.

Contribution

It develops a self-consistent analysis method with improved empirical relations and precise abundance measurements, surpassing previous simple photo-ionization models.

Findings

Achieved 1% error in T([OIII]) measurements

Obtained 5-9% accuracy in oxygen abundance (O/H)

Methodology enhances elemental abundance accuracy in HII galaxies

Abstract

We propose a methodology to perform a self-consistent analysis of the physical properties of the emitting gas of HII galaxies adequate to the data that can be obtained with the XXI century technology. This methodology requires the production and calibration of empirical relations between the different line temperatures that should superseed currently used ones based on very simple, and poorly tested, photo-ionization model sequences. Then, these observations are analysed applying a methodology designed to obtain accurate elemental abundances of oxygen, sulphur, nitrogen, neon, argon and iron in the ionsied gas. Four electron temperatures and one electron density are derived from the observed forbidden line ratios using the five-level atom approximation. For our best objects errors of 1% in T([OIII]), 3% in T([OII]) and 5% in T([SIII]) are achieved with a resulting accuracy between 5 and 9% in total oxygen abundances, O/H. These accuracies are expected to improve as better calibrations based on more precise measurements, both on electron temperatures and densities, are produced.