MOND and the dark baryonsO. Tiret1, 2 and F. Combes1
1 Observatoire de Paris, LERMA, 61 Av. de l'Observatoire, 75014 Paris, France
2 SISSA, via Beirut 4, 34014 Trieste, Italy
Received 3 October 2008 / Accepted 8 January 2009
We consider for the first time the implications for the modified gravity MOND model of galaxies, of the presence of dark baryons, in 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 a0 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 ( m s-2, c = 3), which is also compatible with the one obtained from a second method minimizing the scatter in the baryonic Tully-Fisher relation.
Key words: galaxies: general -- galaxies: kinematics and dynamics -- galaxies: spiral -- galaxies: structure -- cosmology: dark matter
© ESO 2009