Unbiased surveys for dense cloud cores using multi-beam supercondutcing receiver

我们利用两台4米毫米波望远镜进行了大规模的观测，获得了天鹅座、仙后座、蛇夫座、蛇蛇座和金牛座区域^<13>CO （J=1-0）发射的约30万个光谱。观测到的区域相当于整个天空的15%，这使得这次调查在^<13>CO中范围最广。我们已经确定了1000多个^<13>CO云，并分析了这些云的物理参数。通过与IRAS点源的比较，我们考察了各云的恒星形成活动以及新生恒星特征与云特征之间的关系。这是第一次基于如此统一的光谱数据来分析云的特征。结果表明：(1)云的质谱在太阳>>的100-10,000 M_<<范围内以指数-1.7的幂律形式表示。(2)各云内最亮恒星的光度与云的质量之间存在一定的关系；也就是说，恒星的最大光度随着云质量的增加而增加。通过对金牛座区域^<13>CO的详细观测，我们还发现了以下三点：(1)金牛座星云的基本结构是丝状的；(2)恒星的形成发生在柱状密度最高的地方；(3)恒星形成后不久，高密度的分子气体就消失了。我们通过观测比^<13>CO更透明的C^<18>O，详细研究了云的稠密区域，发现上述关系(2)和(3)比^<13>CO更显著。这些结果对于理解分子气体中恒星的形成是有价值的知识。

We have carried out a large-scale survey with two 4 meter millimeter-wave telescopes, and obtained about 300,000 spectra of ^<13>CO (J=1-0) emission toward the Cygnus, Cassiopeia, Ophiuchus, Serpens and Taurus regions. The observed area corresponds to 15% of the whole sky, which makes this survey the most extensive one among those made in ^<13>CO.We have identified more than 1,000 ^<13>CO clouds and analyzed the physical paramerers of these clouds. Comparing with the IRAS point sources, we have examined the star formation activity of each cloud and the relationship between the characteristics of newly-born stars and those of clouds. This is the first time to analyze characteristics of clouds based on such a uniform spectral data. As a result, following two points are found :(1) The mass spectrum of clouds is expressed as a power-law with the index-1.7 in the range 100-10,000 M_<<of sun>>.(2) There is a relationship between the luminosity of the most luminous star within each cloud and the mass of the cloud ; i.e., the maximum stellar luminosity increases with the cloud mass.We have also found the following three points through the detailed ^<13>CO observations toward Taurus region ; (1) the basic structure of the Taurus cloud is filamentary, (2) star formation has taken place where the column density reaches its highest and (3) soon after the formation occurs, high-density molecular gas disappears. We have studied the dense regions of clouds in detail by observations of C^<18>O,which is more transparent than ^<13>CO,and found that above relations (2) and (3) are more significant than in ^<13>CO.These results are valuable knowledge in order to understand the star formation within molecular gas.