年轻恒星形成过程的分子谱线诊断

恒星是宇宙的基本天体，理解恒星的起源和早期演化是天体物理最有举的课题之一，目前了解的恒星形成的一个基本图象是，恒星是由一个足够大质量的星际分子气体云在其其自引力作用下塌缩而形成。在早期塌缩过程中形成一颗原恒星（胚胎），并且伴随该原恒星的吸积盘，原恒星吸积星际介质中的分子物质,通过吸积盘转移到原恒星表面，原恒星的质量随着增大。在吸积过程中也同时伴随物质向外的剧烈喷发，由于盘的存在，这种喷发通常沿垂直于盘的方向进行，出现双极的空间分布。在天文观测上，一种典型的表现是分子气体的外向流，观测表现为从原恒星双极的红蓝移气体运动^1]。由于恒星形成了星际分子中，因此，对星际分子的谱线探测是研究恒星形成的强有力手段，现在已经发现和证认的星际分子总数有一百多种，其中丰富度最高的气体是H2。在所有的星际分子中，丰度仅次于H2的CO分子的转动跃迁谱易激发，相对于星际介质的不透明度小，观测上易于实现，因此，CO分子就成为探索原恒星形成的有力探针，在毫米波段出现的J＝1－0和J＝2－1跃迁变线以及CO同位素的谱线是最常使用的观测探针，八十年代以来又陆续发现了环形分子SiC2,C3H,C3H2及含磷分子PN和CN等，给宇宙中有机世界的探测提供了丰富的线索。我们对恒形成区内存在的低温原恒星天体进行毫米 波射电谱线观测，测量该原恒星周围分子气体的分布，其物理化学参数，以及速度场分布。根据这些测量结果并运用成熟的数量方法，分析正在发生的物理化学过程，特别是原恒星质量外流的过程。根据观测分析结果得出所观测天体的形成和演化状况。

Molecular Spectral Diagnosis of Star Forming Regions

Stars are the basic building blocks of our universe, therefore it is one of the most important research topics in astrophysics to understand the origin and the early evolution of these objects. The current picture is that stars are formed during the collapse of a large enough self gravitating interstellar molecular cloud. The early collapse gives birth to a fetus of a star, which is surrounded by a rotating accretion disk. The proto star accretes interstellar matter through the disk which in turn transfer the accumulated matter to the central proto-star, then the star gets weight during the process. Observation shows that gorgeous ejection of matter always come along with the accretion process. In the presence of disks, these outflows usually escape from the system along the axis of the disk, forming so called bipolar outflows. Typical tracers of these activities are rich molecules such as CO, SiC 2, C 3H, C 3H 2 etc. Observationally, such typical molecular outflows can be detected using Doppler effect by spectroscopic measurements. Using the 13.7 m radio telescope in Delingha station of Purple Mountain Observatory, we performed a survey for 12 low temperature IRAS objects, some of the sources show high velocity properties. Detailed analysis of the Doppler profiles of IRS34 is presented. Star forming activities are clearly seen in this field.