The composition and evolution of comic dust : spectroscopic studies of insterstellar and protoplanetary silicates

Thesis (Ph. D.)--University of Rochester. Department of Physics and Astronomy, 2017.The composition of silicate dust in the diffuse interstellar medium and in protoplanetary disks around young stars informs our understanding of the processing and evolution of the dust grains leading up to planet formation. Here, I discuss the analysis of dust in protoplanetary disks and in the interstellar medium with models of silicate dust that include amorphous and crystalline silicate grains. I describe the modelling of the optical depth along lines of sight toward the extinguished objects Cyg OB2 No. 12 and ζ Ophiuchi, providing evidence for interstellar amorphous silicate dust with stoichiometry intermediate between olivine and pyroxene, which here is simply referred to as “polivene.” I then provide details and results of model fits to the spectra of protoplanetary disks in the Taurus, Ophiuchus, Chamaeleon, NGC 1333, and Serpens star-forming regions. Finally, I discuss correlations between modelled disk properties and their implications for the silicate dust processing and grain growth processes that ultimately lead to planet formation