Dust-to-gas ratio and metallicity in dwarf galaxies

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