CO molecular clouds from the MWISP project

These spectra exhibit steeper slopes and reduced upper limits as R_GC_ increases. The derived scaling relations are M=12.00R_eff_^2.41^+/-0.003^, {sigma}_v_=0.25R_eff_^0.66+/-0.003^, and {alpha}_vir_=37.2M^-0.40+/-0.002^ for the whole outer Galaxy clouds. These scaling relations show slightly steeper correlations observed in more distant locations and notably deviate from Larson's relations.

We find that 44.3% of the molecular mass resides in gravitationally bound structures, a proportion significantly higher than systematic studies from the CfA survey and external galaxies. Moreover, comparisons among different RGC subsamples also reveal a decrease in the amount of bound mass with increasing RGC. The scale length of the molecular disk is estimated to be approximately 2kpc.

These results, based on a constant CO conversion factor of X_CO_=2.0x10^20^cm^-2^(K.km.s^-1^)^-1^, may be slightly altered by variations in XCO. In summary, our findings provide robust evidence for the influence of Galactic evolution on molecular cloud properties, at least in the outer Galaxy region studied.