Nobeyama 45-m Cygnus X CO Survey: II Physical Properties of
  $\mathrm{C^{18}O}$ Clumps
  We report the statistical physical properties of the C$^{18}$O($J=1-0$)
clumps present in a prominent cluster-forming region, Cygnus X, using the
dataset obtained by the Nobeyama 45-m radio telescope. This survey covers 9
deg$^2$ of the north and south regions of Cygnus X, and totally 174 C$^{18}$O
clumps are identified using the dendrogram method. Assuming a distance of 1.4
kpc, these clumps have radii of 0.2-1 pc, velocity dispersions of
$<2.2~\mathrm{km~s^{-1}}$, gas masses of 30-3000 $M_\odot$, and H$_2$ densities
of (0.2-5.5)$\times10^4~\mathrm{cm^{-3}}$. We confirm that the C$^{18}$O clumps
in the north region have a higher H$_2$ density than those in the south region,
supporting the existence of a difference in the evolution stages, consistent
with the star formation activity of these regions. The difference in the clump
properties of the star-forming and starless clumps is also confirmed by the
radius, velocity dispersion, gas mass, and H$_2$ density. The average virial
ratio of 0.3 supports that these clumps are gravitationally bound. The
C$^{18}$O clump mass function shows two spectral index components,
$\alpha=-1.4$ in 55-140 $M_\odot$ and $\alpha=-2.1$ in $>140~M_\odot$, which
are consistent with the low- and intermediate-mass parts of the Kroupa's
initial mass function. The spectral index in the star-forming clumps in
$>140~M_\odot$ is consistent with that of the starless clumps in 55-140
$M_\odot$, suggesting that the latter will evolve into star-forming clumps
while retaining the gas accretion. Assuming a typical star formation efficiency
of molecular clumps (10%), about ten C$^{18}$O clumps having a gas mass of
$>10^3~M_\odot$ will evolve into open clusters containing one or more OB stars.
