Exploring Chemical Evolution from Star Forming Cores to Protoplanetary Disks by Multi-Wavelength Line Survey

在这个项目中，用最先进的射电望远镜研究了与太阳型原恒星周围原恒星盘形成相关的化学演化。为此目的所必需的敏感接收器也已研制并投入使用。主要结果如下：(1)通过谱线测量观测，确定了原恒星包层的化学多样性。(2)通过观测环境气体与原恒星分子流出相互作用形成的激波区，对颗粒地幔的化学成分进行了表征。(3)利用ALMA的亚弧秒观测，首次发现了气体向原恒星流入的离心屏障。发现气体的化学成分在离心屏障处发生了剧烈的变化。(4)在I类原恒星TMC-1A中，发现了分子的不对称分布，这可能是包膜的残余。

In this program, chemical evolution associated with formation of protostellar disks around solar-type protostars has been studied with state-of-the-art radio telescopes. Sensitive receivers necessary for this purpose have also been developed and commissioned. The main outcomes are as follows.(1)Chemical diversity in protostellar envelopes has been established by spectral line survey observations.(2)Chemical compositions of grain mantle have been characterized by observing shocked regions caused by interactions between ambient gas and molecular outflows from protostars.(3)With subarcsecond observations with ALMA, the centrifugal barrier of infalling gas toward the protostar has been identified for the first time. Chemical compositions of the gas are found to change drastically at the centrifugal barrier.(4)In the Class I protostar TMC-1A, an asymmetric distribution of molecules, which is probably a remnant of the envelope, has been identifed.