Variation of α_CO as a function of metallicity compared to Schruba et al. (2012); Sandstrom et al. (2013); Amorín et al. (2016); Madden et al. (2020). The red data points and upper limits are from Madden et al. (2020). We also show on top the most likely solution (empty black circle with the gray circle indicating the standard deviation) with M(H₂) = 10^5.4 M_⊙ and CO 3500 times fainter than in Zhou et al. (2021) and on bottom the secondary, less likely, solution with 10⁷ M_⊙ and CO in agreement with Zhou et al. (2021).