| Abstract |
Aims: We study the resolved stellar populations of dwarf galaxies in the nearby Centaurus A/M 83 group of galaxies. Our goal is to characterize their evolutionary history and to investigate eventual similarities or differences with the dwarf population in other group environments.
Methods: This work presents the analysis of five late-type (irregular) dwarfs found in the vicinity of the giant spiral M 83. Using archival HST/ACS data, we perform synthetic color - magnitude diagram modeling to derive the star formation histories of these late-type dwarfs.
Results: The target objects show heterogeneous star formation histories, with average star formation rates of 0.08 to 0.70 × 10-2 M☉ yr-1. Some of them present prolonged, global bursts of star formation (~300-500 Myr). The studied galaxies are all metal-poor ([Fe/H ] ~ -1.4). We further investigate the spatial extent of different stellar populations, finding that the young stars show a clumpy distribution, as opposed to the smooth, broad extent of the old ones. The actively star forming regions have sizes of ~100 pc and lifetimes of ≳ 100 Myr, thus suggesting a stochastic star formation mode for the target dwarf irregular galaxies. The galaxies formed ~20% to 70% of their stars more than ~7 Gyr ago.
Conclusions: The studied dwarfs have average star formation rates slightly higher than their analogues in the Local Group, but comparable to those in the M 81 group. Our preliminary sample indicates that the neutral gas content of the target dwarfs does seem to be affected by the group environment: galaxies within a denser region have a much lower MHI/ ⟨ SFR ⟩ than the isolated ones, meaning that they will exhaust their gas reservoir more quickly. |
