Exploring an Evolution of Chemical Diversity from Protostellar disks to Protoplanetary disks

现在已经确定低质量的0级原恒星源具有显著的化学多样性。在这项研究中，进一步探讨了这种多样性向原恒星盘和原行星盘的演变。利用Nobeyama 45 m望远镜和IRAM30 m望远镜对多个I类源进行了谱线巡天观测，TMC-1A被确定为具有丰富碳链分子存在特征的WCCC（暖碳链化学）源的I类类似物。同时，利用阿塔卡马大型毫米波/亚毫米波阵列（ALMA）以1”或更高的空间分辨率观测了WCCC源的原型L1527，研究了WCCC源的演化。碳链分子被证实存在于内半径约为100天文单位的落入旋转包络层中，尽管它们在里面是缺乏的。这是了解WCCC源化学演化的重要线索。此外，利用德国马克斯普朗克研究所的100米望远镜，在金牛座分子云中观测到Heiles Cloud 2方向上CH的大尺度分布，以探索WCCC现象的起源。基于这一结果，我对一种可能性进行了严格的测试，即母云中恒星形成的短时间尺度是造成WCCC现象的原因。

It is now established that low-mass Class 0 protostellar sources show significant chemical diversity. In this study, further evolution of such diversity toward protostellar disks and protoplanetary disks has been explored. Spectral line survey observations have been conducted toward various Class I sources with the Nobeyama 45 m telescope and the IRAM30 m telescope, and TMC-1A has been identified as a Class I analog of the WCCC (warm carbon chain chemistry) source which is characterized by rich existence of carbon-chain molecules. In parallel, the evolution of the WCCC source has been studied by observing its prototype, L1527, with high spatial resolution of 1” or better by using ALMA (Atacama Large Millimeter/submillimeter Array). Carbon-chain molecules are confirmed to exist inan infalling rotating envelope whose inner radius is about 100 AU, although they are deficient within it. This is an important clue to an understanding chemical evolution of the WCCC sources. Furthermore, large scale distribution of CH has been observed toward Heiles Cloud 2 in the Taurus molecular cloud by using the Max Planck Institute 100 m telescope in Germany in order to explore an origin of the WCCC phenomenon. On the basis of the result, I have critically tested a possibility that short timescale of star-formation in a parent cloud is responsible for the WCCC phenomenon.