Spiral galaxies rotation curves in the Horava - Lifshitz gravity theory

TL;DR

This study tests a modified Horava-Lifschitz gravity theory against galaxy rotation curves, finding it incompatible with observed data unless unrealistic dark matter halo parameters are assumed, thus challenging the theory's validity.

Contribution

It evaluates the galaxy rotation curve predictions of a modified Horava-Lifschitz gravity theory including dark matter halos, revealing significant inconsistencies with observations.

Findings

Modified gravity alone cannot fit rotation curves.

Unrealistically small halo mass is needed for marginal fit.

Results challenge the validity of the modified theory.

Abstract

We focus on a modified version of Horava - Lifschitz theory and, in particular, we consider the impact of its weak - field static spherically symmetric limit on the galaxy dynamics. In a previous paper, we used the modified gravitational potential obtained in this theory to evaluate the Milky Way rotation curve using a spheroidal truncated power - law bulge and a double exponential disc as the only sources of the gravitational field and showed that the modified rotation curved is not in agreement with the data. Making a step forward, we here include also the contribution from a dark matter halo in order to see whether this helps fitting the rotation curve data. As a test case, we consider a sample of spiral galaxies with smooth baryon matter distribution and well measured circular velocity profiles. It turns out that, although a marginal agreement with the data can be found, this can only be obtained if the dark matter halo has an unrealistically small virial mass and incredibly large concentration. Such results can be interpreted as a strong evidence against the reliability of the gravitational potential obtained in the modified version of Horava -Lifschitz theory that we consider.