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

我们用两台4米毫米波望远镜进行了大范围的观测，获得了天鹅座、仙后座、蛇夫座、蛇夫座和金牛座等区域约30万条~(13)&GT；CO(J=1-0)发射光谱。观测面积相当于整个天空的15%，这是在13&gt；CO进行的调查中范围最广的一次。我们已经识别了1000多个^&lt；13&gt；CO云，并分析了这些云的物理参数。通过与IRAS点源的对比，考察了各星云的恒星形成活动，以及新生恒星特征与星云特征的关系。基于如此均匀的光谱数据分析云的特征尚属首次。结果发现：(1)星云的质量谱在太阳质量指数为-1.7的范围内呈幂函数关系.(2)每颗星云中最亮的恒星的光度与星云的质量有关，即恒星的最大光度随云质量的增大而增大.通过对金牛座地区的详细观测，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)当星柱密度达到最大时，恒星已经形成；(3)形成后不久，高密度的分子气体就消失了。我们通过C^&lt；18&gt；O比^&lt；13&gt；CO更透明的观测，详细地研究了云的致密区，发现上述关系式(2)和(3)比^&lt；13&gt；CO更有意义。这些结果对于理解分子气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.