Stars and ionized gas in UGCA 320: a nearby gas-rich, dwarf irregular galaxy

ABSTRACT UGCA 320 is a gas-rich dwarf irregular galaxy which belongs to a nearby, relatively isolated group of dwarf galaxies. Here, we combine multiband Hubble Space Telescope imaging data with deep long-slit Southern African Large Telescope/Robert Stobie Spectrograph and integral-field Very Large Telescope/Multi Unit Spectroscopic Explorer spectral data to study the stellar and ionized gas components of UGCA 320. Our imaging data analysis reveals a very blue ($V-I\sim 0.1$ mag), flattened radial colour profile. We detect an abundance of ionized gas in UGCA 320 powered mostly by recent star formation. The stellar disc in UGCA 320 is populated predominantly by young (${\sim }120$ Myr) and metal-poor (${\sim}15 \!-\! 30$ per cent solar metallicity) stars and it rotates in the same sense as the ionized gas disc but with higher rotation velocities, and possibly in different planes. Our analysis reveals a sharp transition in the kinematic properties of the discs at radius ${\sim}10 \, {\rm arcsec}$ (${\sim}0.3$ kpc) and distortions in the outer disc region. We show that these features are consistent with a recent tidal interaction, most likely with its close neighbour – UGCA 319. We discuss our results in the context of interacting dwarf galaxies and also show that similar inferences can be made independently from the long-slit data analysis as with the integral-field data.