\label{mvir_mlum} Virial mass, $M_{\mathrm{vir}}$, compared to the luminous mass, $M_{\mathrm{lum}}$, of the GMAs. The data are consistent with the fit line, representing the expected one to one ratio for virial equilibrium. Blue triangles represent nuclear clouds, which are the most massive, green circles represent inter-arm clouds, which are the least massive, and purple diamonds represent arm clouds.