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High angular resolution studies of the structure and evolution of protoplanetary disks

Citation

Eisner, Joshua A (2005) High angular resolution studies of the structure and evolution of protoplanetary disks. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-05262005-141109

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.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:interferometry; planet formation; protoplanetary disks; young stars
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Astronomy
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Hillenbrand, Lynne A.
  • Sargent, Anneila Isabel
Thesis Committee:
  • Sari, Re'em (chair)
  • Sargent, Anneila Isabel
  • Carpenter, John M.
  • Hillenbrand, Lynne A.
  • Kulkarni, Shrinivas R.
Defense Date:17 May 2005
Author Email:jae (AT) astro.caltech.edu
Record Number:CaltechETD:etd-05262005-141109
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-05262005-141109
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2095
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:26 May 2005
Last Modified:26 Dec 2012 02:46

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