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Description
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 data set obtained by the Nobeyama 45m radio telescope. This survey covers 9deg^2^ of the northern and southern regions of Cygnus X, and, in total, 174 C^18^O clumps are identified using the dendrogram method. Assuming a distance of 1.4kpc, these clumps have radii of 0.2-1pc, velocity dispersions of <2.2km/s, gas masses of 30-3000M_{sun}_, and H_2_ densities of (0.2-5.5)x10^4^cm^-3^. We confirm that the C^18^O clumps in the northern region have a higher H_2_ density than those in the southern region, supporting the existence of a difference in the evolutionary 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 55-140M_{sun}_ and {alpha}=-2.1 in >140M_{sun}_, which are consistent with the low- and intermediate-mass parts of the Kroupa's initial mass function. The spectral index of the star-forming clumps >140M_{sun}_ is consistent with that of the starless clumps ranging from 55-140M_{sun}_, 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 10 C^18^O clumps having a gas mass of >10^3^M_{sun}_ will evolve into open clusters containing one or more OB stars.
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