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Title: 円盤形成領域の有機分子
Other Titles: Organic molecules in disk-forming regions
Authors: 大屋, 瑶子1 Browse this author
Authors(alt): Oya, Yoko1
Keywords: 星形成
Star formation
Disk formation
Low-mass protostars
Organic molecules
Chemical evolution
Issue Date: 24-Mar-2020
Publisher: 低温科学第78巻編集委員会
Journal Title: 低温科学
Volume: 78
Start Page: 229
End Page: 239
Abstract: 近年,電波望遠鏡の感度と解像度の向上により,原始星円盤形成領域の化学組成の分布や,天体間 での多様性が明らかにされつつある.若い低質量原始星天体で知られていた化学的多様性が円盤形成 領域まで持ち込まれていることが示され,また単一天体内でも,エンベロープガスから円盤にかけて, ガスの化学組成が急激に変化する様子が見られた.その中で,エンベロープガスでは炭素鎖分子に富 むwarm carbon-chain chemistryの特徴を示し,円盤形成スケールでは飽和有機分子に富むhot corinoの特徴を示す天体(hybrid天体)が,化学進化の標準的なケースであることがわかってきた.これ らの化学的描像は,星形成に伴う化学進化を理解する端緒になると期待される.
Thanks to recent improvements in radio telescopes,chemical structures in disk-forming regions have since been revealed. It is known that young low-mass protostellar sources show chemical diversity on the protostellar corescale. The two representative cases are hot corino sources rich in saturated COMs and warm carbon-chain chemistry (WCCC)sources rich in unsaturated carbon-chain molecules. Such chemical diversity on the protostellar core scale has recently been found to be delivered to disk-forming regions. Moreover,the chemical composition of the gas drastically changes from an infalling envelope to a rotating disk in each source. The hot corino sources and the WCCC sources seem to be the distinct cases, and the hybrid case is likely the standard one for chemical evolution in disk-forming regions; the infalling envelope gas is rich in unsaturated carbon-chain molecules(WCCC-like),whereas the rotating disk is rich in saturated COMs (hot corino-like). Both the chemical diversity and the chemical structure are interpreted in terms of the chemical evolution of grain mantle species. Methane formed by the hydrogenation of atomic carbon on dust grain evaporates in warm regions near protostars and effectively forms carbon-chain molecules. On the other hand,COMs formed from CO on dust grains evaporate in hot regions nearer to protostars. Their relative abundance is thus a key factor for chemical diversity,which is suggested to be a result of environmental effects in the prestellar core phase. These new illustrations of chemical structures will be an important clue to understanding chemical evolution during disk formation.
Type: bulletin (article)
Appears in Collections:低温科学 = Low Temperature Science > 第78巻

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