The all-Galaxy CO survey of is by far the most uniform , large-scale Galactic CO survey .
Using a dendrogram-based decomposition of this survey , we present a catalog of 1064 massive molecular clouds throughout the Galactic plane .
This catalog contains 2.5 \times 10 ^ { 8 } solar masses , or 25 ^ { +10.7 } _ { -5.8 } \% of the Milky Way ’ s estimated \ce H2 mass .
We track clouds in some spiral arms through multiple quadrants .
The power index of Larson ’ s first law , the size-linewidth relation , is consistent with 0.5 in all regions – possibly due to an observational bias – but clouds in the inner Galaxy systematically have significantly ( \sim 30 \% ) higher linewidths at a given size , indicating that their linewidths are set in part by Galactic environment .
The mass functions of clouds in the inner Galaxy versus the outer Galaxy are both qualitatively and quantitatively distinct .
The inner Galaxy mass spectrum is best described by a truncated power-law with a power index of \gamma = -1.6 \pm 0.1 and an upper truncation mass M _ { 0 } = ( 1.0 \pm 0.2 ) \times 10 ^ { 7 } ~ { } \textrm { M } _ { \sun } , while the outer Galaxy mass spectrum is better described by a non-truncating power law with \gamma = -2.2 \pm 0.1 and an upper mass M _ { 0 } = ( 1.5 \pm 0.5 ) \times 10 ^ { 6 } ~ { } \textrm { M } _ { \sun } , indicating that the inner Galaxy is able to form and host substantially more massive GMCs than the outer Galaxy .
Additionally , we have simulated how the Milky Way would appear in CO from extragalactic perspectives , for comparison with CO maps of other galaxies .