Corner plots of best-fit parameters for the log($L{\prime }_{\mathrm{CO}}/{10}^{10}\mathrm{K}\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{pc}}^2)=mlog(L_{\mathrm{FIR}}/{10}^{12}{\mathrm{L}}_{\odot })+b$ relation (see Sect. 5.1) for the full sample (top) and when removing AGN without a match in the control sample (bottom). Results of AGN host galaxies are shown in red, those of non-active galaxies in blue. The contours show the 1–4σ levels, from inner- to outermost, and increase linearly.