The influence of ionized gas kinematics on HII galaxies. The cases of Tol 1004-296 and Tol 0957-278

TL;DR

This study investigates the ionized gas kinematics in two HII galaxies, Tol 1004-296 and Tol 0957-278, revealing how velocity dispersion influences star formation and gas dynamics without clear rotational patterns.

Contribution

It provides new insights into the gas kinematics and star formation processes in BCGs using integral field spectroscopy, highlighting the role of velocity dispersion over rotation.

Findings

No rotation patterns observed in either galaxy.

High velocity dispersion correlates with low metallicity and emission intensity.

Distinct linear velocity dispersion pattern suggests star formation sites push gas in opposite directions.

Abstract

Blue Compact Galaxies (BCGs), also known as \HII\ galaxies, are dwarf, star-forming objects with relatively simple dynamics, which allows for the investigation of star formation mechanisms in a cleaner manner compared to late-type objects. In this study, we have examined various characteristics of the interstellar medium, in connection with the kinematics and dynamics of ionized gas, in Tol 1004-296 and Tol 0957-278. These two objects were observed using the SOAR Integral Field Spectrometer (SIFS) attached to the Southern Observatory for Astrophysical Research (SOAR). Both galaxies were observed with two gratings: one with medium resolution for monochromatic and abundance maps, and another with high resolution for kinematics and profile analysis. Additionally, we conducted an analysis on the velocity and velocity dispersion maps using intensity-velocity dispersion (I - $\sigma$) and velocity-velocity dispersion (Vr - $\sigma$) diagrams. Neither object exhibits a rotation pattern, and only Tol 1004-296 shows a velocity gradient between the two principal knots. However, the study reveals the significant role played by velocity dispersion in the star formation process. Specifically, we identified a relationship between monochromatic intensity, metallicity, and velocity dispersion, where high emission corresponds to low metallicity and low velocity dispersion. Tol 1004-296, in particular, exhibits a distinctive linear high velocity dispersion pattern between the two main knots, suggesting that both star formation sites are pushing the gas in opposite directions.