MOND and the dark baryons

TL;DR

This paper investigates how the presence of dark baryons, in the form of cold molecular gas, affects the MOND model of galaxy rotation curves, leading to a revised critical acceleration and consistent results across different methods.

Contribution

It demonstrates that MOND remains valid with dark baryons, but the critical acceleration parameter is lowered, and provides a quantified relationship between gas content and model parameters.

Findings

MOND models are still valid with dark baryons.

The critical acceleration a0 is reduced to 0.96×10^-10 m/s^2.

Best model parameters are a0=0.96×10^-10 m/s^2 and c=3.

Abstract

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 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 (a0 = 0.96 10e-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.