The Internal Kinematics of the HII Galaxy II Zw 40

TL;DR

This study investigates the internal kinematics of the ionized gas in the giant HII region of galaxy II Zw 40 using high-resolution spectroscopy, revealing the dominant role of gravity and stellar winds in shaping the gas dynamics.

Contribution

It provides a detailed kinematic analysis of II Zw 40's HII region with high spatial and spectral resolution, highlighting the mechanisms behind line broadening and gas motion.

Findings

Gravity and stellar winds dominate line broadening.

The central 50 pc region influences the integrated line profile.

The interstellar medium structure resembles nearby extragalactic HII regions.

Abstract

We present a study of the kinematic properties of the ionized gas in the dominant giant HII region of the well known HII galaxy: II Zw 40. High spatial and spectral resolution spectroscopy has been obtained using IFU mode on the GMOS instrument at Gemini-North telescope. We have used a set of kinematics diagnostic diagrams, such as the intensity vs. velocity dispersion intensity vs. radial velocity, for global and individual analysis in sub-regions of the nebula. We aim to separate the main line broadening mechanisms responsible for producing a smooth supersonic integrated line profile for the giant HII region. The brightest central region (R ~ 50 pc) is responsible for sigma derived from a single fit to the integrated line profile. The dominant action of gravity, and possibly unresolved winds of young (<10 Myr) massive stars, in this small region should be responsible for the characteristic Halpha velocity profile of the starburst region as a whole. Our observations show that the complex structure of the interstellar medium of this galactic scale star-forming region is very similar to that of nearby extragalactic giant HII regions in the Local Group galaxies.