Assignment of v_LSR as a function of λ = 1.1 mm peak flux density. The blue dashed curve in each panel represents the cumulative distribution of flux densities for that subset of sources. Left: velocity assignment fraction for the collection of dense-gas tracers discussed in Section 2.2 over the longitude range of Shirley et al. (2013). The dips in assignment fraction at S_1.1 4 Jy are due to multiple detected velocity components, new V2 sources on the edge of mosaic panels, or source boundary shifts between the V1 and V2.1 catalogs. Right: Galactic longitude further limited to the GRS coverage. Velocity assignment fractions of dense-gas tracers (solid gray) and morphologically extracted ¹³CO spectra (dot–dashed black) are shown, along with the combined velocity assignment fraction (solid black).