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From Molecular Clouds to Our Solar System: An Evolutionary Study of Ice and Dust in Preparation for the James Webb Space Telescope

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Title:From Molecular Clouds to Our Solar System: An Evolutionary Study of Ice and Dust in Preparation for the James Webb Space Telescope
Authors:Chu, Laurie Elizabeth Urban
Contributors:Hodapp, Klaus W. (advisor)
Astronomy (department)
Keywords:Astronomy
Astrochemistry
Ice
Insterstellar Medium
Molecular Clouds
show 2 morePlanetary
Star Formation
show less
Date Issued:2020
Publisher:University of Hawai'i at Manoa
Abstract:Ice and dust play a key role in building the Solar System. During their life cycle, these primitive components are exposed to complex physical and chemical processes. Some of the earliest remnants from the formation of the early Solar nebula still remain in comets providing a way to probe these initial building blocks. As comets travel toward the sun, ices sublimate revealing much about their composition and history. However, the survival of ices in comets is poorly constrained. The comet 49P/Arend-Rigaux is a low-activity periodic comet and was suspected of losing its volatiles (ices) over time. Over several apparitions small tail and jet-like features were observed. Using dust dynamical models I determine the grain properties and the outgassing duration of these different displays of activity. By modeling the ice sublimation over time I show there is a clear decrease in activity over 30 years providing a strong example of a comet transitioning to a dormant state. Outside the Solar System, initial conditions promoting ice formation can be studied within small dense molecular cores where cold surfaces of dust grains become chemical factories for simple and complex ice molecules to form. However it is unclear if complex organic molecule (COM) formation requires energetic UV radiation from newborn stars. To test this, I measure the CO and CH3OH abundances for the first time with lines of sight toward background stars through molecular cores. I find a large abundance of CH3OH ice and a high conversion rate from CO into CH3OH during the pre-stellar phase, signifying that COMs can indeed form in cold environments and account for COMs observed at later stages of star formation. To constrain the local density of hydrogen (H and H2) in the cores where COMs can form, I create very high spatial resolution extinction maps and transform them into three dimensions using an inverse-Abel transformation. Only a small fraction (<~2%) of the volume of the cores have sufficient density for CH3OH and thus presumably other COMs to form. This work is in preparation for large-scale ice maps that will be obtained with the slitless spectroscopy mode of JWST-NIRCAM. I present simulations testing the feasibility of the observations and projected science return.
Pages/Duration:182 pages
URI:http://hdl.handle.net/10125/70341
Rights:All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections: Ph.D. - Astronomy


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