This study presents a catalog of 8107 molecular clouds that covers the entire Galactic plane and includes 98 % of the ^ { 12 } CO emission observed within b \pm 5 ^ { \circ } .
The catalog was produced using a hierarchical cluster identification method applied to the result of a Gaussian decomposition of the Dame et al .
data .
The total H _ { 2 } mass in the catalog is 1.2 \times 10 ^ { 9 } M _ { \odot } , in agreement with previous estimates .
We find that 30 % of the sight lines intersect only a single cloud , with another 25 % intersecting only two clouds .
The most probable cloud size is R \sim 30 pc .
We find that M \propto R ^ { 2.2 \pm 0.2 } , with no correlation between the cloud surface density , \Sigma , and R .
In contrast with the general idea , we find a rather large range of values of \Sigma , from 2 to 300 M _ { \odot } pc ^ { -2 } , and a systematic decrease with increasing Galactic radius , R _ { gal } .
The cloud velocity dispersion and the normalization \sigma _ { 0 } = \sigma _ { v } / R ^ { 1 / 2 } both decrease systematically with R _ { gal } .
When studied over the whole Galactic disk , there is a large dispersion in the line width-size relation , and a significantly better correlation between \sigma _ { v } and \Sigma R .
The normalization of this correlation is constant to better than a factor of two for R _ { gal } < 20 kpc .
This relation is used to disentangle the ambiguity between near and far kinematic distances .
We report a strong variation of the turbulent energy injection rate .
In the outer Galaxy it may be maintained by accretion through the disk and/or onto the clouds , but neither source can drive the 100 times higher cloud-averaged injection rate in the inner Galaxy .