Dynamics of Starbursting Dwarf Galaxies. III. A HI study of 18 nearby objects

TL;DR

This study examines the gas dynamics of 18 nearby starbursting dwarf galaxies using HI observations, revealing their rotation properties, baryonic content, and the impact of star formation on their gas retention.

Contribution

It provides detailed kinematic analysis and rotation curves for starbursting dwarfs, highlighting their baryonic fractions and gas retention despite intense star formation.

Findings

9 galaxies have regular HI disks

Baryons constitute at least 30% of total mass

Starbursts did not significantly eject gas

Abstract

We investigate the dynamics of starbursting dwarf galaxies, using both new and archival HI observations. We consider 18 nearby galaxies that have been resolved into single stars by HST observations, providing their star formation history and total stellar mass. We find that 9 objects have a regularly-rotating HI disk, 7 have a kinematically disturbed HI disk, and 2 show unsettled HI distributions. Two galaxies (NGC 5253 and UGC 6456) show a velocity gradient along the minor axis of the HI disk, that we interpret as strong radial motions. For galaxies with a regularly rotating disk we derive rotation curves, while for galaxies with a kinematically disturbed disk we estimate the rotation velocities in their outer parts. We derive baryonic fractions within about 3 optical scale lengths and find that, on average, baryons constitute at least 30$\%$ of the total mass. Despite the star formation having injected $\sim$10$^{56}$ ergs in the ISM in the last $\sim$500 Myr, these starbursting dwarfs have both baryonic and gas fractions similar to those of typical dwarf irregulars, suggesting that they did not eject a large amount of gas out of their potential wells.