This research is motivated by the need to better understand the role of dust in astrophysical environments. Dust is a vital ingredient in the star formation process as well as in planet forming disks. It is a source of mass loss from evolved stars (through radiation pressure on dust grains) and intimately links the radiation field to the circumstellar material. Dust also contributes to several aspects of interstellar processes such as gas heating and the formation of molecules.
The work to be undertaken here is specifically centered on characterizing the precise nature of dust grains around cool carbon stars as these are the source of the bulk of the Galaxy's carbon-rich dust. By knowing the initial state of the dust from such stars, the effects of the dust in the interstellar medium can be more accurately quantified. Moreover, the relatively benign environment surrounding such stars simplifies the chemistry, which in turn facilitates the understanding of the various processes in operation. The properties of the grains are also tied to the evolution of the star itself, thus the precise nature of the dust must be assessed in order to understand this evolution. Finally, recent Spitzer Space Telescope observations of carbon stars in the Magellanic Clouds suggest a different dust condensation sequence compared to Galactic carbon stars which may well permit the effects of metallicity on dust formation to be investigated.
The tools to be applied here include infrared spectroscopy and imaging, radiative transfer modeling, laboratory spectroscopy, and archival data mining. They will be used to test current theories of dust formation in carbon star environments and how these condensation sequences are effected by the initial mass and metallicity of the parent stars. Furthermore, the imaging and radiative transfer studies should provide insight into the causes of axisymmetric structures seen in planetary and protoplanetary nebulae. This project includes the participation and training of a doctoral student who will be an integral part of the research program. The student will be expected to present results at both conferences and public talks thereby combining training with public outreach.
