Complex molecules, grain chemistry, and the possible detection of interstellar glycine
Miao, Yanti
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https://hdl.handle.net/2142/21327
Description
Title
Complex molecules, grain chemistry, and the possible detection of interstellar glycine
Author(s)
Miao, Yanti
Issue Date
1996
Doctoral Committee Chair(s)
Snyder, Lewis E.
Department of Study
Astronomy
Discipline
Astronomy
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Physics, Astronomy and Astrophysics
Language
eng
Abstract
Glycine $\rm(NH\sb2CH\sb2COOH)$ is the smallest amino acid. Detecting interstellar glycine could shed light on the presolar nebular chemistry and its possible role in seeding newly formed planets with the building blocks of living organisms. This thesis presents the results of the most sophisticated search to date for interstellar glycine.
Chapter 1 reviews the scientific significance of detecting interstellar glycine.
Chapter 2 investigates the possible formation mechanism for interstellar glycine. Like other complex molecules, glycine is expected to be produced on dust grains and then evaporated into the gas phase. Therefore, the young hot molecular cores in star-forming regions may not only somewhat resemble the presolar nebulae but also have a high concentration of large complex molecules including glycine.
Chapter 3 pioneers a new method in which an interferometric array is used for molecular identifications. The unique properties of arrays--large field of view, high angular resolution, and spatial filtering--make them the most powerful instruments for identifying new complex molecules.
Chapters 4 and 5 focuses on the work of discovering an outstanding young hot molecular core, Sagittarius B2(N). This source is rich in large complex molecules such as CH$\sb2$CHCN, HCOOCH$\sb3,$ (CH$\sb3)\sb2$CO, and $\rm CH\sb3CH\sb2CN.$ It was found that the emission from these molecules is confined to a region of $\sim$ 0.2 pc $\times$ 0.3 pc toward Sgr B2(N). No emission was detected elsewhere in the $\rm2\sp\prime\ x\ 2\sp\prime$ mapping field toward Sgr B2. Sgr B2(N) was discovered to be the source for searching for large molecules.
Chapter 6 discusses the detection and confirmation of interstellar acetic acid (CH$\sb3$COOH) in Sgr B2(N), a precursor of glycine in laboratory experiments.
Chapter 7 presents the most promising results ever found. Emission features were detected toward Sgr B2(N), which agree fairly well with the rest frequencies of the $15\sb{0,15}-14\sb{0,14}$ transition and the blended $J=18-17$ transitions of Conformer I glycine. The locations and the velocities of these features are consistent. The proposed identification is also supported by the agreement between the features and the kinematics of the gas in Sgr B2(N).
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