6 Summary

In this paper, we have analysed the relation between dust-to-gas ratio and metallicity of BCDs by using our chemical evolution model. We have focused on the dust destruction process, because this process was not investigated in LF98. We have shown that the dust destruction significantly affects the dust-to-gas ratio when the metallicity is larger than $12+\log{\rm (O/H)}\sim 8$. The intermittent SFH can explain the large variety of dust-to-gas ratio among BCDs through the "dust destruction efficiency'' of $\beta _{\rm SN}$.

Acknowledgements

We thank the anonymous referee for invaluable comments and suggestions which improved this paper very much. We thank A. Ferrara and K. Yoshikawa for useful discussions on dwarf galaxies and excellent environments for our study. We are also grateful to S. Mineshige and J. Silk for continuous encouragement. H. H. was supported by the Research Fellowship of the Japan Society for the Promotion of Science for Young Scientists. We fully utilised the NASA's Astrophysics Data System Abstract Service (ADS).