We consider for the first time the implications on the modified gravity MOND model of galaxies , of the presence of dark baryons , under the form of cold molecular gas in galaxy discs .
We show that MOND models of rotation curves are still valid and universal , but the critical acceleration a _ { 0 } separating the Newtonian and MONDian regimes has a lower value .
We quantify this modification , as a function of the scale factor c between the total gas of the galaxy and the measured atomic gas .
The main analysis concerns 43 resolved rotation curves and allows us to find the best pair ( a _ { 0 } = 0.96 \times 10 ^ { -10 } m.s ^ { -2 } , c = 3 ) , which is also compatible to the one obtained from a second method by minimizing the scatter in the baryonic Tully-Fisher relation .