Histogram over number of galaxies in C ii flux normalised by FIR flux. Light-grey corresponds to galaxies considered HC₃N-poor, medium-gray corresponds to nearby HC₃N-luminous galaxies whose HC₃N/HCN ratios probably are overestimated (see Appendix A.1), dark-grey corresponds to all other HC₃N-luminous galaxies, and white corresponds to galaxies where the upper limit on the HC₃N/HCN ratio is too high to tell whether it is HC₃N-luminous or not. FIR fluxes were calculated from IRAS 60 μm and 100 μm fluxes with the method described in Bizyaev (2001). The references for the used IRAS fluxes are given in the caption of Fig. 10. C ii flux values are from Negishi et al. (2001), except for IC 342 and NGC 3079 (Stacey et al. 1991); IC 860 and NGC 4418 (Malhotra et al. 2001); Arp 220 (Luhman et al. 2003); and NGC 1614 (Brauher et al. 2009).