Towards a full general relativistic approach to galaxies

TL;DR

This paper explores a general relativistic model of spiral galaxy dynamics, extending previous work by including non co-rotating dust, and examines how relativistic effects like dragging influence dark matter interpretations.

Contribution

It generalizes existing models by relaxing co-rotation assumptions, highlighting relativistic effects on galaxy rotation curves and dark matter estimates.

Findings

Non co-rotating dust reduces the energy density needed for galaxy rotation curves.

Relativistic dragging effects can mimic dark matter influences.

Discrepancies between Newtonian gravity and general relativity are emphasized at low velocities.

Abstract

We analyze the dynamics of a single spiral galaxy from a general relativistic viewpoint. We employ the known family of stationary axially-symmetric solutions to Einstein gravity coupled with dust in order to model the halo external to the bulge. In particular, we generalize the known results of Balasin and Grumiller, relaxing the condition of co-rotation, thus including non co-rotating dust. This further highlights the discrepancy between Newtonian theory of gravity and general relativity at low velocities and energy densities. We investigate the role of dragging in simulating dark matter effects. In particular, we show that non co-rotance further reduce the amount of energy density required to explain the rotation curves for spiral galaxies.