演講資訊

摘要：

Dust is an important component of the interstellar medium in galaxies. Although it contributes only about 1% of the mass of the interstellar medium, its influence is far-reaching. The presence of dust in galaxies very efficiently alters the ambient radiation field within galaxies, as it scatters and absorbs starlight, and re-emits it at much longer, infrared, wavelengths. In a typical galaxy, about 30% of the light emitted by stars is reprocessed by dust before escaping the galaxy. In very dusty galaxies, such as Ultraluminous Infrared Galaxies (ULIRGs), which typically exhibit starburst activity, this number can be as high as 90%, thus dramatically altering the spectral energy distribution of galaxies. Indeed, in the distant universe, the dominant detection method for dusty galaxies is detecting their peak SED emission at submillimeter wavelengths. The evolution of the interstellar dust reservoir, and the evolution of the galaxy itself go hand-in-hand, as the presence of dust alters evolutionary drivers, such as the interstellar radiation field and the star formation history, while at the same time, the dust itself is being formed and altered by processes taking place in galaxies. Indeed, dust can often even be used as a tracer of physical conditions. The exact mineralogical composition, the size and the shape of dust grains, are all affected by the physical conditions. Due to the more permanent nature of solids, dust grains provide a historical record of its processing history, while interstellar gas will only ever probe the present conditions. In short, dust remembers, while gas forgets. The properties of dust can be derived using a multitude of observational methods. In particular, spectroscopy in the mid-infrared, using space-based facilities, such as the Infrared Space Observatory (ISO) and Spitzer, has shaped the field of astromineralogy. Additional constraints come from the far-infrared and submillimeter, where the slope of the thermal dust emission traces the grain size. I will discuss the present state of the field, and our recent results on this topic. I will also highlight future observational opportunities open to Taiwanese astronomers to continue the study of interstellar dust in galaxies. I will emphasize the Band 1 receiver for ALMA and the SPICA mission, both projects in which Taiwan has a hardware involvement.