Plateau de Bure spectra of HCN, HCO⁺, HNC 1–0 and HC₃N 10–9. In the right panels we have zoomed-in on the base of the line to show the line wings more clearly. In general, red solid lines show Gaussian fits to the line center (core) line widths and are 197 km s^-1 for HC₃N and HNC, 213 km s^-1 for HCO⁺ and 236 km s^-1 for HCN. However, in the top right panel of HCN 1–0 we instead show two Gaussian fits (one with δV(FWHM) = 180 km s^-1 and one with δV(FWHM) = 870 km s^-1), as discussed in Sect. 3.1. Zero velocity was set for redshift z = 0.042170.