Study on Molecular Cloud Formation by Large scale Submillimeter-wave Observations of Neutral Carbon Atom

在本研究中，我们开发了安装在富士山亚毫米波望远镜上的灵敏接收系统，以进行中性碳原子的大范围测绘观测。在492 GHz和809 GHz分别获得了120K和580K的DSB噪声温度。在天文观测中连续使用的亚毫米波接收器中，这些都是一流的性能。利用这个灵敏的接收器，我们对包括猎户座A巨型分子云和金牛座暗云在内的许多附近的分子云进行了中性碳原子492 GHz谱线的大范围映射观测。此外，我们还首次用中性碳原子的809 GHz谱线绘制了几个具有代表性的恒星形成区。从这些结果中我们发现，中性碳原子的丰度并不强烈地依赖于紫外场强度，而是取决于分子云的演化阶段。

In the present study, we have developed the sensitive receiver system installed on the Mount Fuji submillimeter-wave telescope in order to conduct the large-scale mapping observations of the neutral carbon atom. We achieved the DSB noise temperature of 120 K at 492 GHz and 580 K at 809 GHz. These are the top class performance among the submillimeter-wave receivers continuously used in the astronomical observations.With this sensitive receiver, we have conducted large-scale mapping observation of the 492 GHz line of the neutral carbon atom toward many nearby molecular clouds including Orion A giant molecular cloud and Taurus dark cloud complex. Furthermore, we have mapped several representative star-forming regions with the 809 GHz line of the neutral carbon atom for the first time. From these results, we found that the abundance of the neutral carbon atom is not strongly dependent on the UV field strength, but on the evolutionary stage of molecular clouds.