不同演化阶段的分子云与恒星形成的研究

Molecular Clouds in Different Evolutionary Stages and Star Formation

利用Ｍａｓａｃｈｕｓｅｔｓ－ＳｔｏｎｙＢｒｏｏｋ的１２ＣＯ的分辨率为４７″的银道面巡天和ＩＲＡＳ的分辨率为１５′的红外巡天图像资料，系统地进行了ｌ＝８°～３８°，ｂ＝－１°～＋１°天区内不同分子云演化阶段与恒星形成过程的对比研究．将上述天区划分成３０个小区，通过图像处理，得到了每个小区的ＣＯ（１－０）和波长６０μｍ上远红外发射的空间分布，计算出相应天区的分子云复合体的红外色温度和光深分布，结合ＩＲＡＳ红外点源和ＨＩＩ区星表，把分子云从年轻到年老的演化阶段分成四大类，分析了它们的主要特征以及与恒星形成过程的关系．文章最后对超致密ＨＩＩ区和原恒星候选体沿银经的分布，以及ＨＩＩ区和原恒星候选体与分子云成协的比例进行了统计研究，再次说明在银河系中恒星形成活动仍在不断地发生和进行．

A systematic comparison between molecular clouds in different evolutionary stages and processes of star formation is made over the range of 8° to 38° in Galactic longitude and -1°to +1°in Galactic latitude by using the Massachusetts-Stony Brook Survey data of 12 CO in the Galactic plane(HPFW=47″)and the IRAS Infrared Sky Survey image data(1 5′ per pixel).This region is divided into thirty subregions.Then,the space distribution of CO(1-0) emission and the corresponding infrared intensity at 60μm is obtained for each subregion,and the contours of infrared color temperatures and optical depths of molecular cloud complexes in the corresponding regions are calculated and derived. Moreover,the catalogs of the IRAS infrared point sources and HII regions are used.Thus,molecular clouds in different evolutionary stages are identified and divided into four groups ranging from young clouds to evolved clouds,and their main characteristics and relations to the processes of star formation are analysed.The Galatic-longitude distributions of ultracompact HII regions and candidate protostars as well as the ratio between HII region-molecular cloud and candidate protostar-molecular cloud associations are analysed statistically.The results indicate that star formation activities are currently still going on in our Galaxy.