The Research of Massive Star Forming Regions.

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The study of star formation is a relatively young descipline of the field of astronomy. Though many data to this project now exists, we have not yet produced a viable theory of star formation. Especially for massive star formation, there are many important question which remained unanswered. As the massive star forming region are very far except OMC1, high resolution radio observations are needed to study the dense corse of GMC. Recently high resolution observations are available by using 45m telescope of Nobeyama Radio Observatory. In this project we have observed 5 bright rimmed molecular clouds(NGC281,M17,IC1848,Orion Bright Bar,S140,IC1848) to study the blister model of massive star formation and 5 massive star forming regions to study the evolution of proto massive stellar disk.(W58,W31,W30H,ON1,W33) using 45 m telescope. One frequently cited prescription for a link between molecular clouds and massive star fomation is the blister model of massive star formation, in which massive … More stars form on the surfaces of molecular clouds as a result of external perturbation. For this we observed Orion bright bar. This bar has ideal configuration to study the interaction between HII region and molecular cloud. We found the evidence of shock compressed layer lying parallel to the ionization front. However the apparent density enhancement of 3 in the shocked regions is too small for a radiative shock. In order to explain this discrepancy we proposed a model that the shock compressed region are clumpy or inhomogneous. The observations of M17 also supports this picture. However we can't find the evidence that shocks can compress material enough to trigger star formation.In order to study the evolution of proto stellar disk we observed 5 massive star forming regions. Main results are as follows. 1. In W58 we found a massive proto stellar disk which rotates in a direction parallel to the galactic rotation. Also the velocity gradients of ^<13>CO and HCO^+ emissions suggests differential rotation. 2. Elongated massive structures are found and there are velocity gradient in the direction to the elongation. 3. Every elongated structure has two or three dense cores. 4. Each dense core has a velocity gradient nearly parallel to the elongated structure. We think that this velocity gradient is due to rotation. From these results, we proposed a scenario of the evolution of the proto stellar disk. Less