Dust-to-gas ratio and star formation history of blue compact dwarf galaxies

¹ Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5, 50125 Firenze, Italy
² Department of Astronomy, Faculty of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan e-mail: tajiri, kamaya@kusastro.kyoto-u.ac.jp

Corresponding author: H. Hirashita, irasita@arcetri.astro.it

Received: 25 July 2001
Accepted: 29 March 2002

Abstract

This paper investigates the origin of the observed large variety in dust-to-gas ratio, , among blue compact dwarf galaxies (BCDs). By applying our chemical evolution model, we find that the dust destruction can largely suppress the dust-to-gas ratio when the metallicity of a BCD reaches , i.e., a typical metallicity level of BCDs. We also show that dust-to-gas ratio is largely varied owing to the change of dust destruction efficiency that has two effects: (i) a significant contribution of Type Ia supernovae to total supernova rate; (ii) variation of gas mass contained in a star-forming region. While mass loss from BCDs was previously thought to be the major cause for the variance of , we suggest that the other two effects are also important. We finally discuss the intermittent star formation history, which naturally explains the large dispersion of dust-to-gas ratio among BCDs.