Upper panel: linewidth comparison of stacked mm- and submm-RRLs. The black filled circles indicate sources with a peak flux with S/N ≥ 8 σ of both RRLs. Lower panel: peak flux comparison of stacked mm- and submm-RRL. The black symbols are the same as in the upper panel. The black dashed lines indicate the locus of equal linewidths and fluxes. The blue lines show the best fit from BCES bisector fitting.