Effects of dust extinction on optical spectroscopic properties for starburst galaxies in distant clusters

Recent observational studies on galaxies in distant clusters discovered a s ignificant fraction of possible dusty starburst galaxies with the so-called e(a) spectra that are characterized by strong H delta absorption and relat ively modest [O II] emission. We numerically investigate spectroscopic and photometric evolution of dusty starburst galaxies in order to clarify the o rigin of the e(a) spectra. We found that if a young starburst population is preferentially obscured by dust over an old one in a dusty starburst galax y, the galaxy shows an e(a) spectrum. It is therefore confirmed that the se lective dust extinction, which was first suggested by Poggianti & Wu and me ans that the strongest dust extinction occurs in the youngest among stellar populations with different ages, is critically important to reproduce quan titatively the observed e(a) spectra for the first time in the present nume rical study. We also discuss what physical process is closely associated wi th this selective dust extinction in a cluster environment.