Testing Weyl gravity at galactic and extra-galactic scales

Abstract

We examine the viability of Weyl conformal gravity as an alternative to the general theory of relativity. By using the extended rotation curve of the Milky Way and velocity dispersions of four globular clusters, we show that Weyl gravity predictions without resorting to dark matter comply with observations at the galactic scale. For the Milky Way, we demonstrate that the uncertainty in baryonic modeling results in a bracket of possible rotational velocities which well encompasses the diversity in rotation curve construction. Such diversity generally arises from differences in measurements of velocity anisotropy parameter, and the circular speed and Galactocentric distance of the Sun. Furthermore, we explore the ability of Weyl gravity to account for the inferred acceleration of Abell cluster 1689.