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標題: | 獵戶座星雲中熱微核的普遍性與發源 The Prevalence and Origins of Hot Corinos in the Orion Molecular Cloud Complex |
作者: | 許世穎 Shih-Ying Hsu |
指導教授: | 呂聖元 Sheng-Yuan Liu |
關鍵字: | 天文化學,星際物質,複雜有機分子,熱微核,低質量恆星形成, Astrochemistry,Interstellar medium,Complex organic molecule,Hot corino,Low-mass star formation, |
出版年 : | 2023 |
學位: | 博士 |
摘要: | 在恆星形成區域(SFR)探索複雜有機分子(COM)對於揭示宇宙中生命的起源和普遍性十分重要。而相關研究中,「熱微核」這個主題更為關鍵。「熱微核」是一個在低至中質量的年輕恆星體(YSO)中,一個聚集了溫暖、大量複雜有機分子的局部區域。「熱微核」的形成、演化、分佈等研究,有望於讓我們更加理解「類太陽星雲」中早期的生命化學。
本論文介紹了「ALMASOP」計畫下,針對獵戶座複雜分子雲中的第0類、第I類原恆星的化學調查結果。此研究旨在調查這些原恆星核中,熱微核的普遍性、起源處和物理、化學等特性。先透過低靈敏度、低解析度的觀測資料,發現四顆原恆星擁有熱微核。隨後透過高靈敏度、高解析度的觀測資料,共發現11顆原恆星擁有個熱微核。樣本中的熱微核的檢測率能隨著觀測靈敏度而提升。此外,在相似的觀測條件和天體距離下,不同星雲中的熱微核檢測也相仿。最後,各種複雜有機分子相對於甲醇的豐度與文獻報告一致。 為了進一步揭示熱微核的物理特性和發源處,本研究對第0類、第I類原恆星核進行了光譜能量分佈(SED)建模分析。本研究先是建立了「原恆星溫暖包層質量」與「熱微核可檢測性」之間的關聯。接著藉由觀測與模擬的甲醇影像之間的比較,證明了溫暖包層中複雜有機分子的存在,對於原恆星出現熱微核表徵的必要性。將ALMASOP的結果與現有文獻相結合,本論文認為「熱微核」普遍存在於是第0類、第I類原恆星中。而缺乏熱微核表徵的情況,可能是由於觀測靈敏度不足、溫暖包層質量有限或塵埃不透明度等因素所致。 本論文讓我們更加理解恆星演化早期階段時的化學組成和物理過程,並以觀測的角度,為熱微核在原恆星系統中的普遍性提供支持。 未來更靈敏的調查和全面的光譜掃描,或能進一步幫助我們揭開太空中的生命之謎。 The investigations of complex organic molecules (COMs) in star-forming regions (SFRs) is vital for unraveling the origins and prevalence of life in the universe. Of particular interest is the "hot corino," a localized zone rich in warm and compact COM emission surrounding low- to intermediate-mass young stellar objects (YSOs). Studies, such as the formation, evolution, and distributions, of hot corino may help understand the pre-biotic chemistry in solar-like nebulae. This thesis presents the outcomes of an extensive COM survey conducted as part of the "ALMA Survey of Orion PGCCs (ALMASOP)" project, focusing on Class 0/I protostellar cores within the Orion molecular cloud complex. The study aimed to investigate the presence, origin, and characteristics of hot corinos in these protostellar cores. Through low-sensitivity observations at approximately 2,400 au, four protostars were found to host hot corinos. Subsequent high-sensitivity observations at approximately 140 au unveiled a total of 11 hot corinos, with the relative abundances of various COMs to methanol aligning with literature reports. The detection rate of hot corinos was found to increase toward the same sample as the sensitivity improves.Moreover, detection rate of hot corinos are similar among different clouds under comparable observation conditions and distances. To uncover the underlying physical properties and origin of hot corinos, spectral energy distribution (SED) modeling was applied to Class 0/I protostars with and without hot corino signatures. The analysis establishes a correlation between the detectability of hot corinos and the mass of the warm envelope in the protostar. Furthermore, through the comparison between the simulated and observed methanol images, it was demonstrated that the presence of COMs in the envelope is crucial for the manifestation of the hot-corino signature. The integration of the ALMASOP project findings and the existing literature suggested that hot corinos are a common feature of Class 0/I protostellar cores. However, the absence of a hot corino signature can be attributed to factors such as insufficient observation sensitivity, limited warm envelope mass, or dust opacity. This thesis advances our understanding of the chemical composition and physical processes involved in the early stages of star formation and provides observational support to the prevalence of hot corinos in protostellar systems. A more sensitive survey and a comprehensive spectral scan are anticipated to bring us closer to unveiling the mysteries of life in space. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/88461 |
DOI: | 10.6342/NTU202302210 |
全文授權: | 同意授權(全球公開) |
顯示於系所單位: | 物理學系 |
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