Left panel: example of outflow wing selection by using spectra of ﹩{}^{13}\mathrm{CO}﹩ (gray solid line) and ﹩{{\rm{C}}}^{18}{\rm{O}}﹩ (gray dashed line) for the ATLASGAL clump G032.797+00.191. Blue wings and red wings identification process: (a) scaling the ﹩{{\rm{C}}}^{18}{\rm{O}}﹩ spectrum to ﹩{}^{13}\mathrm{CO}﹩ peak, shown by the red dash-dotted line; (b) fitting a Gaussian to the scaled ﹩{{\rm{C}}}^{18}{\rm{O}}﹩, shown by the blue dotted line; (c) obtaining the ﹩{}^{13}\mathrm{CO}﹩ residual spectra (black solid line) by subtracting the Gaussian fit to the scaled ﹩{{\rm{C}}}^{18}{\rm{O}}﹩ (red dash-dotted line) from ﹩{}^{13}\mathrm{CO}﹩ (gray solid line); (d) blue wings (﹩6.8\mbox{--}11.8\,\mathrm{km}\,{{\rm{s}}}^{-1}﹩) and red wings (﹩16.3\mbox{--}21.8\,\mathrm{km}\,{{\rm{s}}}^{-1}﹩), shown as red cross symbols, can be determined from where the ﹩{}^{13}\mathrm{CO}﹩ residuals are larger than the 3σ line. Here σ is the noise level of the emission-free spectrum. Right panel: example of outflow wing selection toward ATLASGAL clump G028.199−00.049 in which the ﹩{}^{13}\mathrm{CO}﹩ profile shows clear evidence of self-absorption. First, a Gaussian fit to the shoulders of the ﹩{}^{13}\mathrm{CO}﹩ spectra (gray dash-dotted line) and the fitted Gaussian is used as the true peak temperature of the ﹩{}^{13}\mathrm{CO}﹩. This indicates the expected actual peak for the scaled ﹩{{\rm{C}}}^{18}{\rm{O}}﹩ spectra. Then, following the above procedures (a)–(d) blue wings (﹩89.3\mbox{--}95.8\,\mathrm{km}\,{{\rm{s}}}^{-1}﹩) and red wings (﹩98.3\mbox{--}107.3\,\mathrm{km}\,{{\rm{s}}}^{-1}﹩) are thus determined for G028.199−00.049. For more details, please see Figures 2 and 3 in de Villiers et al. (2014).