MOND and the dark baryons

¹ Observatoire de Paris, LERMA, 61 Av. de l'Observatoire, 75014 Paris, France
² SISSA, via Beirut 4, 34014 Trieste, Italy e-mail: tiret@sissa.it

Received: 3 October 2008
Accepted: 8 January 2009

Abstract

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, ), which is also compatible with the one obtained from a second method minimizing the scatter in the baryonic Tully-Fisher relation.