Disk Structure and the Search for Keplerian Rotation around Young High-Mass Stars

Morrison, James (2020) Disk Structure and the Search for Keplerian Rotation around Young High-Mass Stars. Master's Thesis / Essay, Astronomy.

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Abstract

High-Mass stars (defined as 8 solar masses or greater) are keystone components in the fields of astrophysics and astrochemistry. However, many questions remain about their formation as they are less numerous and deeply embedded in their envelopes. In this thesis, we investigate the formation of high-mass young stellar objects (YSOs) via circumstellar accretion disks in Keplerian rotation, by means of ALMA archive data. Using methyl cyanide (CH3CN) as a tracer, gas structure and kinematics are determined for nine YSOs. Peak temperatures range from 400 – 700 K, column densities from 1-7x10^16 cm-2, and volume densities > 10^7 cm-3. We determine five disk structures to be in partial or strong Keplerian rotation, with flared morphologies. CH3CN abundances are then compared to chemical models, determining evolutionary timescales of 20-25 kyr, and suggesting the highest abundances from the most massive YSOs. Continuum data is used to determine disk masses, ranging from 1 – 25 solar masses. Toomre stability is analyzed, finding highest stability in those with the strongest Keplerian rotation signatures. A final classification is made of the disks, with six different variations of rotation and structure determined in the sample.

Item Type:	Thesis (Master's Thesis / Essay)
Supervisor name:	Tak, F.F.S. van der
Degree programme:	Astronomy
Thesis type:	Master's Thesis / Essay
Language:	English
Date Deposited:	02 Jul 2020 13:16
Last Modified:	02 Jul 2020 13:16
URI:	https://fse.studenttheses.ub.rug.nl/id/eprint/22377

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