Giant HII Regions in NGC 7479 & NGC 6070

TL;DR

This study investigates the kinematic properties of giant HII regions in two galaxies, revealing complex velocity structures and their influence on luminosity-velocity dispersion relations.

Contribution

It provides high-resolution spectral analysis of HII regions, identifying multiple kinematic components and their effects on established astrophysical correlations.

Findings

Detection of supersonic velocity dispersions in all observed regions.

Identification of multiple kinematic components, including narrow and broad features.

Complex profile structures can significantly affect the interpretation of luminosity-velocity relations.

Abstract

We present new results from our search for Giant H\,{\sc ii} Regions in galaxies visible from the southern hemisphere. In this work we study two galaxies: NGC\,7479 and NGC\,6070. Using high-resolution spectra, obtained with different instruments at Las Campanas Observatory, we are able to resolve the emission-line profile widths and determine the intrinsic velocity dispersion of the ionised gas. We detect profile widths corresponding to supersonic velocity dispersions in the six observed H\,{\sc ii} regions. We find that all of them show at least two distinct kinematical components: a relatively narrow feature (between ~11 and ~22\kms) and a broader (between ~31 and ~77\kms) component. Two of the regions show a complex narrow profile in all ion lines, which can be further split into two components with different radial velocities. Whereas the wing broadening of the overall profile can be fitted with a low-intensity broad component for almost all profiles, in one region it was better reproduced by two separate shell-like wings. We have analysed the impact that the presence of multiple components has on the location of the H{\sc ii} regions in the $\log(L) - \log(\sigma)$ plane. Although the overall distribution confirms the presence of a regression, the precise location of the regions in the plane is strongly dependent on the components derived from the profile fitting.