CO SLED built with the available data for the BCG and the CGM tail of MACS1931 (red and orange stars, respectively). The CO line fluxes are taken from Fogarty et al. (2019), except ¹²CO(7−6) of the BCG which is detected in this work using APEX. Line fluxes are normalised to the ¹²CO(1−0) flux taken from Fogarty et al. (2019). Additional average CO SLEDs from the literature are added for comparison: ULIRGs from Papadopoulos et al. (2012a, blue circles), SMGs from Bothwell et al. (2013, green circles), BzK galaxies from Daddi et al. (2015, purple circles), low-redshift Herschel galaxies from Kamenetzky et al. (2016, magenta circles), and quasars from the QFeedS sample published in Molyneux et al. (2023, cyan circles). The dashed black line shows the theoretical CO SLED for resolved objects with Σ_SFR = 0.83 M_⊙ yr⁻¹ kpc⁻² modelled by Narayanan & Krumholz (2014). This value is the estimated Σ_SFR for the MACS1931 BCG (Fogarty et al. 2015). The grey shaded area shows the predicted CO SLED range with this model for 0.6 < Σ_SFR [M_⊙ yr⁻¹ kpc⁻²] < 3. We report an upper limit on the ¹²CO(7−6) flux for the tail in Table 2, however, it is not constraining the tail CO SLED and falls out of the range of this plot.