X-ray clusters of galaxies in conformal gravity

TL;DR

This study tests conformal gravity as an alternative to dark matter for explaining X-ray galaxy clusters, finding it reproduces some density profiles but fails to match observed temperature distributions.

Contribution

The paper provides the first simulation-based assessment of conformal gravity's ability to explain galaxy cluster properties without dark matter.

Findings

Density profiles fit beta-models similar to observations

Temperature predictions are significantly higher than observed

Temperature profiles increase with radius, contrary to real clusters

Abstract

We run adiabatic N-body/hydrodynamical simulations of isolated self-gravitating gas clouds to test whether conformal gravity, an alternative theory to General Relativity, is able to explain the properties of X-ray galaxy clusters without resorting to dark matter. We show that the gas clouds rapidly reach equilibrium with a density profile which is well fit by a beta-model whose normalization and slope are in approximate agreement with observations. However, conformal gravity fails to yield the observed thermal properties of the gas cloud: (i) the mean temperature is at least an order of magnitude larger than observed; (ii) the temperature profiles increase with the square of the distance from the cluster center, in clear disagreement with real X-ray clusters. These results depend on a gravitational potential whose parameters reproduce the velocity rotation curves of spiral galaxies. However, this parametrization stands on an arbitrarily chosen conformal factor. It remains to be seen whether a different conformal factor, specified by a spontaneous breaking of the conformal symmetry, can reconcile this theory with observations.