http://arxiv.org/abs/2102.12499
We test whether refracted gravity (RG), a modified theory of gravity that describes the dynamics of galaxies without the aid of dark matter, can model the dynamics of the three massive elliptical galaxies, NGC 1407, NGC 4486, and NGC 5846, out to $\sim$$10R_{\rm e}$, where the stellar mass component fades out and dark matter is required in Newtonian gravity. We probe these outer regions with the kinematics of the globular clusters provided by the SLUGGS survey. RG mimics dark matter with the gravitational permittivity, a monotonic function of the local mass density depending on three paramaters, $\epsilon_0$, $\rho_{\rm c}$, and $Q$, that are expected to be universal. RG satisfactorily reproduces the velocity dispersion profiles of the stars and red and blue globular clusters, with stellar mass-to-light ratios in agreement with stellar population synthesis models, and orbital anisotropy parameters consistent with previous results obtained in Newtonian gravity with dark matter. The sets of three parameters of the gravitational permittivity found for each galaxy are consistent with each other within $\sim$1$\sigma$. We compare the mean $\epsilon_0$, $\rho_{\rm c}$, and $Q$ found here with the means of the parameters required to model the rotation curves and vertical velocity dispersion profiles of 30 disk galaxies from the DiskMass survey (DMS): $\rho_{\rm c}$ and $Q$ are within 1$\sigma$ from the DMS values, whereas $\epsilon_0$ is within 2.5$\sigma$ from the DMS value. This result suggests the universality of the permittivity function, despite our simplified galaxy model: we treat each galaxy as isolated, when, in fact, NGC 1407 and NGC 5846 are members of galaxy groups and NGC 4486 is the central galaxy of the Virgo cluster.
V. Cesare, A. Diaferio and T. Matsakos
Fri, 26 Feb 21
44/60
Comments: 22 pages, 12 figures, 8 tables. Submitted to A&A