open access

https://doi.org/10.14943/lowtemsci.78.229

https://hdl.handle.net/2115/77787

Organic molecules in disk-forming regions

日本語

Chemical evolution

2020-03-24

低温科学第78巻編集委員会

低温科学

78

229-239

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.

紀要論文

Version of Record

1880-7593