CO SLED of our post-SB galaxies flux ratio. Individual galaxies are shown with small colored circles (measurements) and down-pointing triangles (3σ upper limits), while the average SLED is indicated by empty red circles. For comparison, we also show the Milky Way SLED (black squares; Carilli & Walter 2013), the average SLED of main-sequence galaxies (filled black triangles from Valentino et al. 2020 and empty black triangles from Boogaard et al. 2020), and the SLED predicted by the model of Narayanan & Krumholz (2014) assuming a SFR surface density of Σ_SFR = 0.05 M_⊙ yr⁻¹ kpc⁻² (blue diamonds) and Σ_SFR = 500 M_⊙ yr⁻¹ kpc⁻² (pink diamonds).