A statistical study of star formation by an extensive survey of molecular clouds

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It is one of the most important subjects of modern astronomy to understand how stars are formed in interstellar space. Considerable efforts have been made toward the understanding of star formation processes. However, most young stars detected so far are optically visible or have high far infrared luminosities. This suggests that the view on star formation we have at present might be significantly biased toward the later stage of star formation and thus toward the massive star formation. We should have an unbiased sample of star formation regions in order to correctly understand star formation, particularly in it earliest stage heavily obscured in molecular clouds. In order to obtain unbiased molecular data of star formation regions, the Nagoya group has been surveying the molecular gas within 1-2 kpc of the sun by using the two 4m radio telescopes. This survey covers an area of a few 100 square degrees and is one of the most extended fully samples arc min in the J=1-0 CO, ^<13>CO and … More C^<18>O spectra at 3 mm. The results are discovery of 60 molecular outflows associated with cold IRAS sources, and numerous dense cloud cores in the J=1-0 C^<18>O and J=2-1 CS spectra. This certainly demonstrates that there are a number of star formation regions veiled from previous studies.In the present research, on the basis of the observational data with the Nagoya telescopes, we obtained following four results ; 1. discovery of five molecular outflows including one in the southern sky, 2. a detailed study of correlation in intensity between millimeter wave ^<13>CO and far infrared radiation, 3. a study of the correlation length of the velocity field in a dense core, and 4. a study of the large scale distribution of atomic hydrogen around dark cloud complexes. In addition these, we have marked an important step toward an extensive CO survey in the southern sky in the near future by using the instruments in Australia and Chile.The molecular outflows discovered are located in a dark cloud complex near an HII region IC5146, and near HH132 in the southern sky. Particularly, the IC5146 region was observed for the first time to such an extensive manner in three spectra, CO, ^<13>CO, and C^<18>O, with the Nagoya 4m telescope and with the 14m telescope at University of Massachusetts. This region will provide another good example of active star formation within a dense cloud complex similar to the L1641 cloud. Less