Studying the evolution of dwarf galaxies can provide insights into the characteristics of systems that can act as building blocks of massive galaxies .
This paper discusses the history of star formation and gas flows ( inflow and outflow ) of a dwarf irregular galaxy in the Local Group , NGC 6822 , from the viewpoint of gas-phase and stellar chemical abundance .
Gas-phase oxygen abundance , stellar metallicity distribution and gas fraction data are compared to chemical evolution models in which continuous star formation and gas flows are assumed .
If the galaxy is assumed to be a closed or an accretion-dominated system where steeper stellar initial mass functions are allowed , the observed gas-phase oxygen abundance and gas fraction can be explained simultaneously ; however metallicity distributions predicted by the models seem to be inconsistent with the observed distribution , which suggests that the star formation , gas flows and/or chemical enrichment are more complex than assumed by the models .
When NGC 6822 is assumed to be a system dominated by outflow , the observed values of gas-phase oxygen abundance and gas fraction can be explained , and the metallicity distributions predicted by some of the models are also roughly consistent with the observed distribution in the metallicity range of -2.0 \lesssim [ Fe/H ] \lesssim - 0.5 .
It should be noted that this result does not necessarily mean that the accretion of gas is completely ruled out .
More observables , such as chemical abundance ratios , and detailed modelling may provide deeper insight into the evolution of the system .