The impact on the general properties of HII galaxies in the local universe of the visibility of the [OIII]l 4363 line

TL;DR

This study analyzes how the presence of the [OIII]4363 line affects the observed properties of local HII galaxies, revealing differences in luminosity, metallicity, and ionization, and comparing them to intermediate-redshift Luminous Compact Blue Galaxies.

Contribution

It provides a comprehensive statistical comparison of HII galaxies with and without the [OIII]4363 line, highlighting their physical differences and implications for galaxy evolution.

Findings

Galaxies without [OIII]4363 are more luminous and metal-rich.

Objects without the auroral line have lower ionization and possibly lower temperature star clusters.

Intermediate-redshift LCBGs resemble local HII galaxies lacking the [OIII]4363 line.

Abstract

We present a statistical study of a very large sample of HII galaxies taken from the literature. We focus on the differences in several properties between galaxies that show the auroral line [OIII]l4363 and those that do not present this feature in their spectra. It turns out that objects without this auroral line are more luminous, more metal-rich and present a lower ionization degree. The underlying population is found to be much more important for objects without the [OIII]l 4363 line, and the effective temperature of the ionizing star clusters of galaxies not showing the auroral line is probably lower. We also study the subsample of HII galaxies whose properties most closely resemble the properties of the intermediate-redshift population of Luminous Compact Blue Galaxies (LCBGs). The objects from this subsample are more similar to the objects not showing the [OIII]l 4363 line. It might therefore be expected that the intermediate-redshift population of LCBGs is powered by very massive, yet somewhat aged star clusters. The oxygen abundance of LCBGs would be greater than the average oxygen abundance of local HII galaxies.