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

在本研究中，我们已经开发了灵敏的接收系统安装在富士山亚毫米波望远镜，以进行大规模的中性碳原子的测绘观测。在492 GHz和809 GHz下分别实现了120 K和580 K的DSB噪声温度。利用这台灵敏的接收机，我们对猎户座A巨分子云、金牛座暗星云复合体等附近的许多分子云进行了中性碳原子492 GHz谱线的大尺度成图观测。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依赖于紫外光场的强度，但在分子云的演化阶段。

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.