  We present the results of C18O observations by the Nobeyama Millimeter Array
toward dense clumps with radii of ~ 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, and
0.5 to 54.1 Mo, 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 H2
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 H2 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 H2 density structure and the turbulent motion
of the clump.
