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Type of Document	Dissertation
Author	Eisner, Joshua A
Author's Email Address	jae AT astro.caltech.edu
URN	etd-05262005-141109
Persistent URL	http://resolver.caltech.edu/CaltechETD:etd-05262005-141109
Title	High angular resolution studies of the structure and evolution of protoplanetary disks
Degree	PhD
Option	Astronomy
Advisory Committee	Advisor Name Title Re'em Sari Committee Chair Anneila Isabel Sargent Committee Member John Carpenter Committee Member Lynne A. Hillenbrand Committee Member Shrinivas Ramchandra Kulkarni Committee Member
Keywords	interferometry protoplanetary disks planet formation young stars
Date of Defense	2005-05-17
Availability	unrestricted
Abstract Young stars are surrounded by massive, rotating disks of dust and gas, which supply a reservoir of material that may be incorporated into planets or accreted onto the central star. In this dissertation, I use high angular resolution observations at a range of wavelengths to understand the structure, ubiquity, and evolutionary timescales of protoplanetary disks. First, I describe a study of Class I protostars, objects believed to be at an evolutionary stage between collapsing spherical clouds and fully-assembled young stars surrounded by protoplanetary disks. I use a Monte Carlo radiative transfer code to model new 0.9 micron scattered light images, 1.3 mm continuum images, and broadband spectral energy distributions. This modeling shows that Class I sources are probably surrounded by massive protoplanetary disks embedded in massive infalling envelopes. For the best-fitting models of the circumstellar dust distributions, I determine several important properties, including envelope and disk masses, mass infall rates, and system inclinations, and I use these results to constrain the evolutionary stage of these objects. Second, I discuss observations of the innermost regions of more evolved disks around T Tauri and Herbig Ae/Be stars, obtained with the Palomar Testbed and Keck Interferometers. I constrain the spatial and temperature structure of the circumstellar material at sub-AU radii, and demonstrate that lower-mass stars are surrounded by inclined disks with puffed-up inner edges 0.1-1 AU from the star. In contrast, the truncated inner disks around more massive stars may not puff-up, indicating that disk structure depends on stellar properties. I discuss the implications of these results for disk accretion, terrestrial planet formation and giant planet migration. Finally, I put these detailed studies of disk structure into a broader context by constraining the mass distribution and evolutionary timescales of circumstellar disks. Using the Owens Valley Millimeter Array, I mapped the millimeter continuum emission toward >300 low-mass stars in the NGC 2024 and Orion Nebula clusters. These observations demonstrate that the average disk mass in each cluster is comparable to the "minimum-mass protosolar nebula", and that there may be disk evolution on one million year timescales.
Files	Filename       Size       Approximate Download Time (Hours:Minutes:Seconds)     28.8 Modem   56K Modem   ISDN (64 Kb)   ISDN (128 Kb)   Higher-speed Access    cv.pdf 35.39 Kb 00:00:09 00:00:05 00:00:04 00:00:02 < 00:00:01   thesis.pdf 6.49 Mb 00:30:02 00:15:27 00:13:31 00:06:45 00:00:34