A comparative study of star-forming dwarf galaxies using the UVIT

Abstract

We present a far-ultraviolet (FUV) study of 16 star-forming dwarf galaxies (SFDGs) using the Ultra Violet Imaging Telescope. Morphologically, SFDGs are classified as dwarf spirals, dwarf irregulars, and blue compact dwarfs (BCDs). We extracted the star-forming complexes (SFCs) from the sample galaxies, derived their sizes, and estimated the FUV + 24 μm star-formation rates (SFRs). We also determined the approximate stellar disc mass associated with the SFCs using Infrared Array Camera 3.6 micron images. We derived the specific SFRs (sSFRs), as well as the SFR densities [Σ(SFR)] for the SFCs. We find that the lower Σ(SFR) for each type is different, with the dwarf irregulars having the lowest Σ(SFR) compared with others. However, the median size of the SFCs in the dwarf irregulars is the largest compared with the other two types when compared at roughly the same distance. We have derived the star-forming main sequence (SFMS) on the scale of SFCs for all three classes of SFDGs. We find that although all SFDGs approximately follow the global SFMS relation, i.e. SFR ∝ M*α (where globally α ≈ 1 for low-surface brightness galaxies and 0.9 for SFDGs), on the scale of SFCs the α value for each type is different. The α values for dwarf spirals, dwarf irregulars, and BCDs are found to be 0.74 ± 0.13, 0.87 ± 0.16, and 0.80 ± 0.19, respectively. However, the age of all SFCs approximately corresponds to 1 Gyr. Finally, we find that the outer SFCs in most galaxies except BCDs have a high sSFR, supporting the inside-out model of galaxy growth.