Lyman-alpha Tracing Molecules as a Probe of Protoplanetary Disk Mass 38 views

This thesis investigates whether Lyman-α-sensitive molecular ratios can be used as diagnostics of protoplanetary disk mass. Using a grid of astrochemical models, a computational pipeline was developed to compute disk-averaged column densities and construct tracer/non-tracer molecular ratios. The log10(HCN/CS) ratio was analyzed across a range of disk masses. The distribution shifts systematically across disk mass bins, with lower-mass disks exhibiting more positive ratio values. This indicates that the ratio is sensitive to disk mass and exhibits a measurable trend. However, the distributions show a large intrinsic scatter of ∼ 1 dex, leading to significant overlap between disk mass regimes. Multivariate regression and partial residual analysis show that, while disk mass is the dominant driver of the ratio, additional physical parameters, including UV radiation, cosmic ray ionization rate, and settling environment introduce secondary variability. These results show that Lyα tracer ratios capture global trends in disk mass but are not reliable standalone tracers due to competing physical dependencies. This result demonstrates that, in systems with multiple coupled physical parameters, multivariate regression is required to isolate and quantify individual dependencies, even when the overall trend is preserved in marginal distributions.

BS (Bachelor of Science)

Lyman-alpha; Protoplanetary Disk; Disk mass; Multivariate Regression

English

2026-05-09