Dissertation/Thesis Abstract

Interstellar Molecules in Extreme and Circumstellar Environments
by Anderson, Julie Katelyn, Ph.D., The University of Arizona, 2019, 133; 13902545
Abstract (Summary)

Chemical principles and tools were used to study three phases of the interstellar medium: circumstellar envelopes, shocks from a planetary nebula, and an exploding region of dense gas. First, theoretical principles and instrumentation for the astrochemical research is presented. Then, the chemistry of circumstellar envelopes is investigated. Several microwave and millimeters transitions for the rotational spectrum of CCN (X2Π½) were measured in the lab allowing for the long-searched for detection of CCN in the circumstellar envelope of IRC+10216. The radial abundance of CCN and related species was modeled to elucidate the organic chemistries of the outer envelope. Additionally, PN and PO were detected in the envelopes of three O-rich stars, IK Tau, R Cas, and TX Cam. The radial abundance for PN and PO was modelled in these stars as well as for the O-rich supergiants VY CMa and NML Cyg. In all sources, PO and PN had an abundance ratio of roughly 10:1 and depleted near 100 R*. PN and PO likely participate in chemical networks of the inner envelope for O-rich stars, possibly seeding out onto grains in extended regions from the stars. Finally, extreme interstellar environments were chemically probed. The appearance of CH+ around the young planetary nebula NGC 7027 had been an enigma. An investigation of emission from CH+, C+, and CO reveal that CH+ is likely generated in the H2* shock region, revealing complexity in the organic chemistry of planetary nebulae. Spectral maps of Band 8 and Band 9 emission from HCN, HCO+, and SiO for the Orion-KL region reveal dense, hot, and shocked molecular gas across the nebula. This region continues to show a complexity of its molecular and physical network, showing that chemistry is as far reaching as are the depths of space.

Indexing (document details)
Advisor: Ziurys, Lucy
Commitee: Bieging, John, Shirley, Yancy, Schwartz, Steven
School: The University of Arizona
Department: Chemistry
School Location: United States -- Arizona
Source: DAI-B 81/2(E), Dissertation Abstracts International
Subjects: Physical chemistry, Astronomy, Astrophysics
Keywords: Astrochemistry, Circumstellar chemistry, ISM: abundances, ISM: molecules, Millimeter-wave direct absorption, NGC 7027
Publication Number: 13902545
ISBN: 9781085648066
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