談話会案内

日時

2013年5月9日(木) 15:00

場所

大輪講室

講演者

平下　博之（ＡＳＩＡＡ、台湾）

題目

Evolution of dust abundance and grain size distribution in high-redshift galaxies

要旨

Dust formation and evolution are important components in the understanding of galaxy evolution. In particular, the grain size distribution strongly influences the absorption and emission coefficients in the interstellar medium. We model the evolution of grain size distribution by including some relevant processes: dust production in stellar ejecta (especially supernovae), shattering in interstellar turbulence, and coagulation and accretion in dense clouds. By applying our models to high-redshift (z > 5) galaxies, we find that these processes are efficient enough within the short cosmic ages. Moreover, we show that the observed extinction curves in high-z quasars can be reproduced if the dust supplied from supernovae is processed by shattering in interstellar turbulence. We also calculate the evolution of grain abundance and compare our theoretical results with the observed dust abundances in high-z quasars. We find (i) that grain growth by accretion is crucial to explain the large dust content in high-z quasars, and (ii) that shattering plays a fundamental role in activating grain growth since small-grain production by shattering raises the grain growth rate significantly. These two points are also supported by our more comprehensive models developed recently.