Ionized gas velocity dispersion in nearby dwarf galaxies: looking at supersonic turbulent motions

TL;DR

This study investigates ionized gas turbulence in nearby dwarf galaxies, revealing expanding shells, potential supernova remnants, and the relationship between turbulent motions and star formation processes using Fabry-Perot interferometry.

Contribution

It introduces a method combining I-sigma diagrams and 2D velocity dispersion maps to analyze turbulent motions and identify expanding shells in dwarf galaxies.

Findings

Identified expanding shells with diameters of 80-350 pc and ages of 1-4 Myr.

Found a candidate luminous blue variable star in UGC 8508.

Linked high velocity dispersion regions to diffuse low-density gas around star-forming areas.

Abstract

We present the results of ionized gas turbulent motions study in several nearby dwarf galaxies using a scanning Fabry-Perot interferometer with the 6-m telescope of the SAO RAS. Combining the `intensity-velocity dispersion' diagrams (I-sigma) with two-dimensional maps of radial velocity dispersion we found a number of common patterns pointing to the relation between the value of chaotic ionized gas motions and processes of current star formation. In five out of the seven analysed galaxies we identified expanding shells of ionized gas with diameters of 80-350 pc and kinematic ages of 1-4 Myr. We also demonstrate that the I-sigma diagrams may be useful for the search of supernova remnants, other small expanding shells or unique stars in nearby galaxies. As an example, a candidate luminous blue variable (LBV) was found in UGC 8508. We propose some additions to the interpretation, previously used by Munoz-Tunon et al. to explain the I-sigma diagrams for giant star formation regions. In the case of dwarf galaxies, a major part of the regions with high velocity dispersion belongs to the diffuse low surface brightness emission, surrounding the star forming regions. We attribute this to the presence of perturbed low density gas with high values of turbulent velocities around the giant HII regions.