Date of Award

8-2010

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Physics

Advisor

Brittain, Sean

Committee Member

Leising , Mark

Committee Member

King , Jeremy

Committee Member

Meyer , Bradley

Abstract

This dissertation includes high-resolution, near-infrared spectroscopy to study CO in circumstellar disks around Herbig Ae/Be stars. The velocity-resolved spectra was used to measure the distribution of gas in the circumstellar disk and thus determine the evolutionary state of the system. Near-infrared spectra were obtained on over 30 young circumstellar disks around Herbig Ae/Be stars to study the physical processes in the disk. The radial location of the CO emitting gas bears directly on the evolutionary state of the transition objects in the sample. This study included a detailed study of the debris disk star β Pictoris where the disk mass was estimated. The study found that CO is detected in most disks, yet there were no systems showing evidence for the grain growth scenario of planet formation.
In addition, by using high-resolution spectra of the fundamental ro-vibrational CO emission lines, one can measure the position centroid of the emission as a function of velocity to provide an independent measurement of M(1/2) sin(i) and the disk inclination. Knowing the inclination is crucial for determining the radial distribution of gas inferred by other high-resolution spectra using low spatial resolution instruments such as the Heterodyne Instrument for the Far Infrared on Herschel. Perhaps most importantly, by measuring the position centroid of the emission, one can determine where in the disk the CO emitting gas arises independent of assumptions about the disk velocity field, Keplerian or otherwise. This analysis was performed on HD~100546, where asymmetric emission is observed. The results also provide a fundamental test of our fluorescence emission model, which allows our model to infer the CO emission radii in systems that are too distant to spatially resolve the emission.

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