張慶瑞臺灣大學：天文物理研究所黃昱瑾Huang, Yu-ChinYu-ChinHuang2007-11-262018-06-282007-11-262018-06-282007http://ntur.lib.ntu.edu.tw//handle/246246/52027　　本論文中，我們探討NGC 7027的分子成份。　NGC 7027是年輕且廣泛被研究的行星狀星雲，但至今沒有在3毫米和1.3毫米波段的光譜線普查。　從2005年四月起，我們用亞利桑那電波觀測站(Arizona Radio Observatory)的12米和10米望遠鏡，針對3毫米波段(72-95 GHz)和部份1.3毫米波段(220-243 GHz & 246-266 GHz)做光譜線普查。總共觀測到39條光譜線，分別來自7個已知的星際間分子，6個氫復合線(recombination lines)和一個未辨識出的譜線。　觀測到的分子包含CO和CO的同位素；CN，ＨCN和C2H的超精細結構躍遷譜線；還有離子態分子如HCO＋，N2H＋，和CO＋。　由觀測的資料，可以研究存在於NGC 7027中的分子，並了解過去說明NGC 7027物理環境的研究報告。　光譜線普查結果顯示，NGC 7027中間區域為游離態，還有光化學非常活耀的光化區域(photodissociation region)。　此外，NGC 7027的研究是屬於一個大的光譜線普查計畫，這個計畫目標是觀測IRC+10216，CIT 6，CRL 2688，和NGC 7027。　這四個源分別橫跨漸近巨星分支狀態(asymptotic giant branch phase)，原行星狀星雲狀態(proto-planetary nebula phase)，和行星狀星雲狀態(planetary nebula phase)。　這個觀測結果能進一步研究由漸進巨星分支狀態到行星狀星雲狀態的演化過程。In this thesis, we investigate the molecular content of the NGC 7027, the young and extensively studied planetary nebula for which there is no spectral line survey covering the whole 3mm band and 1.3mm band. Since April 2005, we have carried out the spectral line survey in the 3 mm band (72-95 GHz) and part of 1.3 mm band (220-243 GHz and 246-266 GHz) using the Arizona Radio Observatory (ARO) 12m and 10m telescopes. We detect 39 lines from 7 known interstellar molecules, 6 hydrogen recombination lines and one unidentified line. The detected molecules include CO, and its isotopomers, hyperfine transitions of CN, HCN, C2H, and molecular ions, HCO+, N2H+ and CO+. By using our data, we study the molecular content of NGC 7027 and understand the physical environment as proposed in previous studies. Moreover, the spectral lines show characteristics of ionized central region, and the presence of photodissociation region, where photochemistry is very active. Besides, our study on NGC 7027 is part of a bigger survey project, which aims to observe IRC+10216, CIT 6, CRL 2688, and NGC 7027. These four sources span the asymptotic giant branch(AGB)phase, the proto-planetary nebula phase, and the planetary nebula(PN) phase respectively. The result will allow us to study the chemical evolution from AGB phase to PN phase.Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv 1 Introduction 1 1.1 Stellar Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2 Planetary Nebulae . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.3 Young Planetary Nebula : NGC 7027 . . . . . . . . . . . . . . . . . . 7 2 Observations and Data Reductions 10 2.1 Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.1.1 Kitt Peak 12m Telescope (KP-12m) . . . . . . . . . . . . . . . 15 2.1.2 Heinrich Hertz 10m Telescope (HHT) . . . . . . . . . . . . . 15 2.2 Data Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.2.1 Procedure for Data Reduction . . . . . . . . . . . . . . . . . . 16 2.2.2 Line Identification . . . . . . . . . . . . . . . . . . . . . . . . 17 3 Results of The Spectral Survey 19 3.1 Observed Characteristics of Molecular Lines . . . . . . . . . . . . . 19 3.2 Column Density of Molecules . . . . . . . . . . . . . . . . . . . . . . 30 3.3 Characteristics of Recombination Lines . . . . . . . . . . . . . . . . 31 4 Discussions 36 4.1 The Chemistry of NGC 7027 . . . . . . . . . . . . . . . . . . . . . . . 36 4.2 Comparison of NGC 7027With IRC+10216 . . . . . . . . . . . . . . 37 4.3 Recombination Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 5 Conclusion 43 A Calculations 45 A.1 Radiative Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 A.2 Derivation of Column Density . . . . . . . . . . . . . . . . . . . . . . 46 B Spectra of The Line Survey 491508974 bytesapplication/pdfen-US譜線確認譜線譜查恆星:漸近巨星分支行星狀星雲:單一星雲(NGC 7027)環星物質line identificationsurveysstars : AGBplanetary nebulae : individual(NGC 7027)circumstellar matterotherhttp://ntur.lib.ntu.edu.tw/bitstream/246246/52027/1/ntu-96-R93244009-1.pdf