An Approach to Search for the Proto-Star Forming Regions

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In this research we have studied the high and low mass star formation mechanisms.In order to study massive star formation we have observed the molecular cloud associated with W58, W31, ONI, W33 and W30H by using the 45 m telescope and NRO interferometer. Our observations revealed the clumpy structure with various size in the molecular cloud. This suggests that the dense cores formed in the giant molecular cloud due to the gravitational collapses proceed to fragment and finally collapse into star. This suggests the hierarchical fragmentation. However size distribution doesn't seem to be continuous but discrete with the ratio of 1 to 5 in size. These results are not consistent with the hierarchical fragmentation by cloud turbulence.Another research is to study the low mass star formation. There is little doubt that the solar system was born from a disk of gas and dust encircling the Sun five billion years ago. Recent infrared observations suggest that young stars have dust disks with a m … More ass of 0.001 to 1 Mo (Beckwith et al. 1990). The T-Tauri stars with dust disk have ages ranging from 10^5 to 10^8 year. There are now two models of the formation of the solar system, i. e., Cameron's model (1978), and the Kyoto models (1975). According to Kyoto model, the nebular gas must remain until the formation of Uranus (10^8year). So we have a possibility to find the solar nebular gas toward these T-Tauri stars. We calculate the CO emission from the proto-solar nebula by solving transfer equation assuming the above two models. The calculated antenna temperature is sufficiently high and detectable with 45 m telescope at Nobeyama.We made a survey for CO J=1-0 molecular line emission toward 12 T-Tauri stars in the Taurus dark clouds and 3 Vega type stars nearest to the Sun. T-Tauri stars are predominantly solar mass with ages ranging from 10^5 to 10^8 yr and Vega type stars are in main sequence. We could not detect the nebular gas toward all stars we tried. Our sensitivity was not sufficient to detect the gas of T-Tauri stars because of whether condition. However it is enough to detect if the nebula gas were existed for Vega type stars. So it become clear that the nebula gas is not existed to main sequence stars with dust disk. Less