Dynamics of disk and elliptical galaxies in Refracted Gravity

We investigate the dynamics of galaxies with Refracted Gravity (RG), a novel classical theory of modified gravity inspired to electrodynamics in matter, which does not resort to dark matter. The presence of dark matter is mimicked by a gravitational permittivity, a monotonic increasing function of the local mass density which depends on three universal parameters.

RG properly describes the rotation curves and the vertical velocity dispersions of 30 disk galaxies from the DiskMass Survey (DMS) with mass-to-light ratios consistent with stellar population synthesis (SPS) models, disk scale heights in agreement with edge-on galaxies observations, and RG parameters from individual galaxies consistent with each other, suggesting their universality. RG produces a Radial Acceleration Relation of DMS galaxies with the correct asymptotic limits but with residuals correlating with some galaxy properties and with a too large intrinsic scatter, at odds with observations. Further investigation is required to assess if this issue indicates a failure of RG or depends on the galaxy sample.

RG also models the velocity dispersions of stars and of blue and red globular clusters of the elliptical E0 galaxies NGC 1407, NGC 4486, and NGC 5846 belonging to the SLUGGS survey with mass-to-light ratios in agreement with SPS predictions, anisotropy parameters consistent with the literature, and the three RG parameters in agreement with each other. Two out of three RG parameters are also consistent with those estimated from the DMS galaxies.

Given these encouraging results, RG is a theory that deserves further investigation.