Dust‐to‐Gas Ratio and Metallicity in Dwarf Galaxies

We examine the dust-to-gas ratio as a function of metallicity for dwarfgalaxies [dwarf irregular galaxies (dIrrs) and blue compact dwarf galaxies(BCDGs)]. Using a one-zone model and adopting the instantaneous recyclingapproximation, we prepare a set of basic equations which describes processes ofdust formation and destruction in a galaxy. Four terms are included for theprocesses: dust formation from heavy elements ejected by stellar mass loss,dust destruction in supernova remnants, dust destruction in star-formingregions, and accretion of heavy elements onto preexisting dust grains. Solvingthe equations, we compare the result with observational data of nearby dIrrsand BCDGs. The solution is consistent with the data within the reasonableranges of model parameters constrained by the previous examinations. This meansthat the model is successful in understanding the dust amount of nearbygalaxies. We also show that the accretion rate of heavy element ontopreexisting dust grains is less effective than the condensation of heavyelements in dwarf galaxies.Comment: 14 pages LaTeX, 4 figures, to appear in Ap