Characterization of molecular gas substructures in the protoplanetary disk HD 163296 using ALMA interferometric data
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2024
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Abstract
This thesis conducts an extensive examination of molecular gas substructures, specifically HCN and C2H, within the protoplanetary disk surrounding HD 163296. Utilizing ALMA interferometric data in two rotational transitions, the study resolves structures down to 10 au scales, focusing on characterizing gas substructures and comparing them with millimeter dust in the disk. The methodology involves parameterizing relative abundance, incorporating Gaussian functions, and employing MCMC analysis to model observed bright ring substructures. The study reveals three bright line emission rings for both HCN and C2H, indicating a high abundance within 150 au of the central star. Interestingly, no universal connection is found between dust and molecular substructures, suggesting complex dynamics. The inner disk (<150 au) exhibits a peak relative abundance of ∼6.8 × 10−11 for HCN and ∼5.0 × 10−11 for C2H, implying active organic chemistry or hidden molecular emissions. Furthermore, a significant overlap between dust and chemical substructures within 150 au is observed, diminishing in the outer disk. The outermost bright rings at approximately 309 and 385 au for HCN and C2H respectively lack correlation with CO substructures, challenging conventional understanding of protoplanetary disk composition and dynamics. Chemical conversion of CO into other species is proposed as a partial explanation for observed vertical substructures and high C/O ratios influencing C2H and HCN abundance. This research enhances our understanding of complex dynamics and chemical processes in protoplanetary disks, providing valuable insights for future planet formation studies.
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Tesis (Master of Science in Astrophysics)--Pontificia Universidad Católica de Chile, 2024