大质量恒星形成核区的特性：^(12)CO、^(13)CO和C^(18)O的谱线观测及统计比较  

Characteristics in Massive Star-forming Molecular Cores: Observation and Statistical Study of ^(12)CO, ^(13)CO and C^(18)O Emission

作　　者：张丽云[1] 高煜[1] 

机构地区：[1]中国科学院紫金山天文台,南京210008

出　　处：《天文学报》2008年第2期144-158,共15页Acta Astronomica Sinica

基　　金：国家杰出青年基金项目(编号10425313)资助项目

摘　　要：利用青海站的13.7米射电望远镜对河内24个与水脉泽源成协并有红外Spitzer数据的巨分子云核进行^(12)CO(J=1→0),~913)CO(J=1→0)和C^(18)O(J=1→0)的同时成图观测,平均的成图范围为8′×8′.并全部探测到了C^(18)O的谱线发射,其中11个源有较大范围(5′—8′)的C^(18)O成图,这些分子云核均观测到C^(18)O(J=1→0)谱线积分强度极大值的一半处,其余的13个源由于信噪比低或者成图范围较大等原因,没有进行如此大面积的成图观测.对样本中的11个已成图的稠密核进行了云核特性的分析并统计比较了CO与^(13)CO,^(13)CO与C^(18)O及CO与C^(18)O谱线积分强度之比(R_(12/13) R_(13/18),R_(12/18)),结果是,C^(18)O是光学薄的,可以探测到云核更加细致的结构.从核中心到边缘,3种谱线积分强度比是逐渐增加的.CO与^(13)CO的谱线积分强度比R_(12/13)的范围在2—6之间;^(13)CO与C^(18)O的比值R_(13/18)范围在4—20之间波动,中心区域其值大部分集中在6—12之间,变化范围波动不是很大;CO与C^(18)O之比R_(12/18)在13—90更大的范围内,在更加致密的云核中心该比值集中在13—50之间.With the 13.7m millimeter wave telescope of Purple Mountain Observatory at the Qinghai Station,simultaneous observations of ^12C0, ^13C0 and C^180 line emission were carried out towards 24 Galactic high-mass star forming cores which were associated with water masers and surveyed by the Spitzer. All of them were detected in C^180 lines with the average map size of about 8＇×8＇ In our sample 11 cores were mapped within the regions where C^18O integrated intensity reaches the half maximum,while the rest were not observed with so large scale of mapping because of the low SNR or the intrinsically extended morphology of the cores. HCN and CS molecules are widely used as tracers of dense gas due to their high critical density. However HCN and CS are always optically thick, while ^13C0 is mostly optically thin and C^18O is absolutely optically thin, which make us able to detect innermost to the core of molecular cloud. On the other hand, there has been few big-scale survey of C^18O recently, therefore we just execute mapping comparison, especially mapping of optically-thin molecule C^18O to study inside characteristics of molecular cloud, which supplies useful reference for subsequent observation and research to the molecule C^18O with telescope of higher sensitivity. We discussed the characteristics and the integrated intensity ratios of ^12CO to ^13CO （R12/13）, ^13CO to ClSO （R13/18） and ^12CO to C^18O （R12/l8） statistically towards the 11 fully mapped dense cores in our sample. We concluded that as a tracer of of high column density of the dense gas, C^18O is absolutely optically thin and can detect the detailed structure of the cores. In general, these three ratios gradually increase from the innermost to the outer part of the cores. We found that the integrated intensity ratio R12/13 ranges from 2 to 6; RI3/I8 4 to 20 with a small fluctuation of 6--12 in the inner part of the cores; R12/18 13--90, and typically 13--50 in the denser regions of the cores. Our later work is going to statistically compar

关 键 词：恒星 形成 星际介质 谱线 恒星 发射线 星际介质 分子 

分 类 号：P155[天文地球—天文学]