Banzatti, AndreaSanchez, Michael A.2021-08-122021-08-122021-08Sánchez, M. A. (2021). <i>A study of protoplanetary disk evolution in infrared CO</i> (Unpublished thesis). Texas State University, San Marcos, Texas.https://hdl.handle.net/10877/14296The inner radii (< 10 AU) of protoplanetary disks (PPDs) are the birthplaces of exoplanets. Understanding what happens at these planet-forming distances requires the knowledge of inner gaseous disk evolution. Carbon monoxide (¹²CO; hereafter CO) gas is known to be an effective tracer of excited molecular gas at small radii (0.01 AU – 10 AU). Therefore, in this work, the depletion of molecular gas is traced as the planet-forming regions of PPDs evolve and become gas-poor. To probe CO gas properties, a LTE (local thermal equilibrium) molecular excitation model is employed. Spectral emission of CO and H₂ (molecular hydrogen) gas are compared to analyze gas properties in both gas-rich, full disks and gas-poor transition disks. This approach demonstrates a radial stratification of molecular gas: CO lines are increasingly narrower than H2 lines for disks with large inner gaps, or cavities, suggesting a recession of CO gas in the inner disk. In this thesis, I report results from an excitation analysis of CO spectra to identify how inner disk gas properties change as inner dust cavities form.Text66 pages1 file (.pdf)enProtoplanetary disksEmission spectroscopyAstronomyAstrophysicsThesis