Corner plot of the posterior distribution obtained from the MERCURIUS FIR fitting for J154506 at z = 3.7515 shown in Fig. 6 before correcting for magnification under a self-consistent scenario. Derived values for the dust mass (M_dust), opacity transition wavelength (λ₀), dust temperature (T_dust), and dust emissivity index (β_IR) are shown. Solid grey lines indicate the median (i.e. 50th percentile) of the parameter’s marginalised posterior distribution, while dashed lines show the 16th and 84th percentiles. In panels with the dust temperature, a dotted line indicates T_CMB at the redshift of J154506 (T_CMB = 12.95 K). We note that the total IR luminosity (L_IR) is not an independent parameter of the fitting routine, and is included purely for visualisation purposes.