Effects of dust extinction on optical spectroscopic properties for starburst galaxies in di.pdf

Effects of dust extinction on optical spectroscopic properties for starburst galaxies in distant clusters Yasuhiro Shioya 0 Astronomical Institute, Tohoku University, Sendai, 980-8578, Japan 0 0 2 and g u A Kenji Bekki 7 1 Division of Theoretical Astrophysics, National Astronomical Observatory, Mitaka, Tokyo, 1 181-8588, Japan v 2 6 2 Received ; accepted 8 0 0 0 / h p - o r t s a : v i X r a – 2 – ABSTRACT Recent observational studies on galaxies in distant clusters discovered a significant fraction of possible dusty starburst galaxies with the so-called ‘e(a)’ spectra that are characterized by strong Hδ absorption and relatively modest [OII] emission. We numerically investigate spectroscopic and photometric evolution of dusty starburst galaxies in order to clarify the origin of the e(a) spectra. We found that if a young starburst population is preferentially obscured by dust than an old one in a dusty starburst galaxy, the galaxy shows e(a) spectrum. It is therefore confirmed that the selective dust extinction, which is first suggested by Poggianti Wu (2000) and means the strongest dust extinction for the youngest stellar population among stellar populations with different ages, is critically important to reproduce quantitatively the observed e(a) spectra for the first time in the present numerical study. We furthermore discuss what physical process is closely associated with this selective dust extinction in cluster environment. Subject headings: galaxies: clusters – galaxies: