A spherical scalar-tensor galaxy model

TL;DR

This paper develops a spherical galaxy model within scalar-tensor gravity, explaining observed rotation curves and luminosity profiles, and predicts shallow dark matter density profiles at galactic centers.

Contribution

It introduces a new scalar-tensor galaxy model that fits observational data and predicts specific dark matter distributions influenced by scalar fields.

Findings

Scalar field affects dark matter distribution in galaxies.

Model fits observed stellar rotation velocities.

Predicts shallow density profiles in galactic centers.

Abstract

We build a spherical halo model for galaxies using a general scalar-tensor theory of gravity in its Newtonian limit. The scalar field is described by a time-independent Klein-Gordon equation with a source that is coupled to the standard Poisson equation of Newtonian gravity. Our model, by construction, fits both the observed rotation velocities of stars in spirals and a typical luminosity profile. As a result, the form of the new Newtonian potential, the scalar field, and dark matter distribution in a galaxy are determined. Taking into account the constraints for the fundamental parameters of the theory (lambda,alpha), we analyze the influence of the scalar field in the dark matter distribution, resulting in shallow density profiles in galactic centers.