Abstract

I investigate the dynamics of galaxies in refracted gravity (RG), a novel theory of modified gravity which does not resort to dark matter (DM). The DM presence is mimicked by a gravitational permittivity, a monotonic increasing function of the local mass density that depends on three, in principle, universal parameters. RG reproduces the kinematic profiles of 30 disk galaxies in the DiskMass Survey (DMS), with mass-to-light ratios in agreement with stellar population synthesis models, disk-scale heights consistent with edge-on galaxies observations, and the RG parameters from the individual galaxies in agreement with one another, suggesting their universality. RG models the radial acceleration relation of the DMS galaxies with the correct asymptotic limits but with residuals correlating with some galaxies properties and with a too large intrinsic scatter, in contrast with observations, which requires further investigation. RG also describes the velocity dispersions of stars and of blue and red globular clusters in three elliptical E0 galaxies from the SLUGGS survey with sensible mass-to-light ratios and anisotropy parameters and with the three RG parameters consistent with one another. These parameters are also in agreement with the mean RG parameters estimated from the individual DMS galaxies.

Highlights

  • I investigate the dynamics of galaxies in refracted gravity (RG), a novel theory of modified gravity which does not resort to dark matter (DM)

  • We investigated the dynamics of disk and elliptical galaxies with Refracted Gravity (RG) [1,2], a novel classical theory of modified gravity inspired to electrodynamics in matter, which does not resort to dark matter

  • Further studies are required to assess whether this issue is due either to a fundamental problem of RG, namely Equation (1) is wrong, or to a limitation of Equation (6) for the gravitational permittivity, or to our approximated model, where the galaxies are assumed to be isolated and their interacting environment is not taken into account

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Summary

Introduction

We investigated the dynamics of disk and elliptical galaxies with Refracted Gravity (RG) [1,2], a novel classical theory of modified gravity inspired to electrodynamics in matter, which does not resort to dark matter. We model the rotation curves and the vertical velocity dispersions perpendicular to the galaxy disks from the mass distributions of 30 disk galaxies in the DMS We describe their mass density profiles with a stellar disk, a spherical stellar bulge and an atomic and a molecular gas component. To model the mass density of the stellar disk, ρd(R, z), we adopt a linear interpolation of its measured surface brightness, Id(R), to properly reproduce the observed features of the rotation curve, following the Renzo’s rule [7]. We multiply this profile by a declining exponential profile along the z-direction perpendicular to the disk plane, obtaining: ρd(R, z). To derive the RG gravitational potential, φ, from the mass density ρ(R, z) (Equation (11)) of each galaxy, we numerically solve the RG Poisson Equation (1) with a successive over relaxation Poisson solver, detailed in (Appendix B of [2])

Rotation Curves
Rotation Curves and Vertical Velocity Dispersion Profiles
A Unique Combination of RG Parameters
The Radial Acceleration Relation
Results
Conclusions
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