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

Abstract

We present the results of an ionized gas turbulent motions study in several nearby dwarf galaxies using a scanning Fabry–Perot interferometer with the 6‐m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS). Combining the ‘intensity–velocity dispersion’ diagrams () 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 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 Muñoz‐Tuñón et al. to explain the 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 H ii regions.

Ionized gas rotation curves in nearby dwarf galaxies

“…DDO 125. The Hα image is flocky, numerous expanding shells are identified in it (Moiseev & Lozinskaya, 2012). At the same time, radial velocities are in a reasonable agreement with the circular rotation model.…”

“…DDO 53. We have earlier discovered several expanding shells in this galaxy (Moiseev & Lozinskaya, 2012). At the first glance, the velocity field looks chaotic.…”

“…According to the results of profile approximations, we have built the ionized gas line of sight velocity fields and line of sight velocity dispersion maps as well as the images of galaxies in the Hα emission line and in the continuum. Some of these maps for seven galaxies of our list have already been presented in our previous paper (Moiseev & Lozinskaya, 2012), where we discuss the features of distribution of the ionized gas velocity dispersion.…”

“…A well-known blue compact galaxy with numerous ionized shells around the star forming regions (Simpson et al, 2011;Moiseev & Lozinskaya, 2012, ibid the references to earlier work). PA 0 , i 0 were taken according to the photometric estimate of Simpson et al (2011).…”

Kinematics of Haro 11: The miniature Antennae

“…Turbulence from feedback: it has been debated whether emission line widths are due to virial motions or turbulence created through feedback from star formation (Terlevich & Melnick 1981;Green et al 2010;Moiseev & Lozinskaya 2012). The fact that stellar and gas velocity dispersions tend to agree in Haro 11 argues against turbulent feedback driving the gas velocity dispersion.…”