Dust-to-Gas Ratio and Metallicity in Dwarf Galaxies

We examine the dust-to-gas ratio as a function of metallicity for dwarf galaxies [dwarf irregular galaxies (dIrrs) and blue compact dwarf galaxies (BCDGs)]. Using a one-zone model and adopting the instantaneous recycling approximation, we prepare a set of basic equations which describes processes of dust formation and destruction in a galaxy. Four terms are included for the processes: dust formation from heavy elements ejected by stellar mass loss, dust destruction in supernova remnants, dust destruction in star-forming regions, and accretion of heavy elements onto preexisting dust grains. Solving the equations, we compare the result with observational data of nearby dIrrs and BCDGs. The solution is consistent with the data within the reasonable ranges of model parameters constrained by the previous examinations. This means that the model is successful in understanding the dust amount of nearby galaxies. We also show that the accretion rate of heavy element onto preexisting dust grains is less effective than the condensation of heavy elements in dwarf galaxies.