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恒星形成区的云核和星团

期刊名称：天文学报
时间：0
页码：357-373
分类：P154[天文地球—天文学]
作者机构：[1]中国科学院紫金山天文台,南京210008, [2]中国科学院研究生院,北京100049
相关基金：国家自然科学基金项目（10873037）资助致谢感谢紫金山天文台青海观测站全体工作人员在观测中给予的支持和帮助.
相关项目：宇宙中的恒星形成和起源

关键词：星际介质:云, 恒星:形成, 星际介质:谱线与谱带, 恒星:主序前, ISM： clouds, stars： formation, ISM： lines and bands, stars： pre-main sequence

中文摘要：

利用青海站13．7m毫米波望远镜对17个与星团成协的恒星形成区进行了^12CO（J=1—0）、^13CO（J=1—0）和C^18O（J=1—0）的同时成图观测．除了IRAS 04547＋4753，这些源均探测到较强的C^18O（J=1—0）的谱线发射．由于分子云的大小不同，有13个源观测到^13CO（J=1—0）谱线积分强度极大值的一半处，其他源因分子云延展范围较大，没有进行大面积的成图观测．基于观测数据，计算了各云核的谱线线宽、亮温度、尺度、密度和质量等，^13CO和C^18O云核的维里质量与局部热动平衡（LTE）质量之比分别为0．66和0．74，它们接近于维里平衡状态．为了从形态方面比较云核与星团，将谱线的积分强度图与2MASS的K波段图像叠加．同时，计算了与云核成协的星团的大小和质量，数据采用了2MASS的近红外点源测光结果．基于云核与星团的质量结果，计算了分子云的恒星形成效率，大致在10％～30％的范围．

英文摘要：

Data of （J = 1 - 0） lines of ^12CO, ^13CO and C^18O were taken simultaneously by using 13.7 m millimeter telescope of Qinghai station of Purple Mountain Observatory at Delingha. We map 17 star forming regions which are associated with the clusters. All but IRAS 04547＋4753 show C^18O emission, 13 regions where ^13CO integrated intensities reach the half maximums are fully mapped, while some cores of the other four regions may be missed because of the wide extension of the molecular clouds. Based on the data, some physical properties have been derived, such as the full width at half maximum （FWHM） of three lines, excitation temperature and optical depth. The column density, local thermodynamic equilibrium mass （MLTE） and virial mass （Mvir） have also been obtained. The average ratios of Mvir to MLTE for ^13CO and C^18O cores are 0.66 and 0.74, respectively, suggesting these cores are close to virial equilibrium. The maps of integrated intensities of ^13CO and C^18O are overlaid on the 2MASS K band images to compare the cores with clusters in morphology. We also calculate the sizes and masses of clusters from the photometric results of point sources released by 2MASS database. Based on the result, the star formation efficiency （SFE） of clouds associated with young clusters is calculated. SFE varies over a wide range, from 10% to 30%.