Observations of large biologically important interstellar and cometary molecules.

摘要

There has been much interest in recent years in astronomical searches for large biologically-important molecules which possess known millimeter wavelength transitions. Biologically-important species include amino acids, possible precursors to amino acids, and other biologically interesting molecules. This thesis continued the search for large biomolecules towards hot molecular cores (HMCs) associated with ultracompact (HC) HII regions and comets.; First, we followed up the detection of acetic acid (CH₃COOH) towards Sgr B2(N-LMH) by performing a survey of transitions with large line strengths toward several hot core regions. There has been great interest in searching a variety of star forming regions for interstellar acetic acid because it shares common structural elements with glycine (NH₂CH₂ COOH), the simplest amino acid, and because it is an isomer to both methyl formate (HCOOCH₃) and glycolaldehyde (CH₂OHCHO). In our survey we detected two new sources of acetic acid and placed constraints on the detectability of acetic acid elsewhere with current generation radio telescopes.; Second, in order to study the physical conditions that lead to the formation of large biomolecules toward HMCs, we observed the hot core regions W51 e1 and e2 using the symmetric top species methyl cyanide (CH₃CN). Symmetric tops have properties that make them ideal probes of hot molecular cores. Thus, we obtained better measurements of the physical conditions present in these regions and a better understanding of the chemistry that forms large molecular species.; Third, using multiply degenerate transitions in both the 3 mm and 1 mm wavelength regions, we conducted the most extensive survey for the elusive biomolecule urea [(NH₂)₂CO] toward the high mass hot molecular core sources, Sgr B2(N-LMH) and W51 e2. As a result, our spectral line data support the first detection of interstellar urea toward Sgr B2(N-LMH).; Finally, we discuss the observational results of an extensive survey for biologically interesting molecules toward Comet Hale-Bopp (1995 O1). To date, no large biomolecule has ever been reported toward a comet with an array. The importance of detecting large biomolecules in comets is that in doing so will tie together the chemistry in HMCs with cometary chemistry.