We present the results of C ^ { 18 } O observations by the Nobeyama Millimeter Array toward dense clumps with radii of \sim 0.3 pc in six cluster-forming regions including massive ( proto ) stars .
We identified 171 cores , whose radius , line width , and molecular mass range from 0.01 to 0.09 pc , 0.43 to 3.33 km s ^ { -1 } , and 0.5 to 54.1 M _ { \sun } , respectively .
Many cores with various line widths exist in one clump , and the index of the line width–radius relationship of the cores and the parental clump differs from core to core in the clump .
This indicates that the degree of dissipation of the turbulent motion varies for each core in one clump .
Although the mass of the cores increases with the line width , most cores are gravitationally bound by the external pressure .
In addition , the line width and the external pressure of the cores tend to decrease with the distance from the center of the clump , and these dependencies may be caused by the inner H _ { 2 } density structure of the clump that affects the physical properties of the cores .
Moreover , the number density of the cores and the number density of young ( proto ) stars have a similar relationship to the average H _ { 2 } density of the clumps .
Thus , our findings suggest that the cluster is formed in the clump through the formation of such multiple cores , whose physical properties would have been strongly related to the H _ { 2 } density structure and the turbulent motion of the clump .