Testing Weyl geometric gravity with the SPARC galactic rotation curves database

Abstract

We present a detailed investigation of the properties of the galactic rotation curves in the Weyl geometric gravity model, in which the gravitational action is constructed from the square of the Weyl curvature scalar, and of the strength of the Weyl vector. The theory admits a scalar-vector tensor representation, obtained by introducing an auxiliary scalar field. By assuming that the Weyl vector has only a radial component, an exact solution of the field equations can be obtained, which depends on three integration constants, and, as compared to the Schwarzschild solution, contains two new terms, linear and quadratic in the radial coordinate. In the framework of this solution we obtain the exact general relativistic expression of the tangential velocity of the massive test particles moving in stable circular orbits in the galactic halo. We test the theoretical predictions of the model by using 175 galaxies from the Spitzer Photometry \& Accurate Rotation Curves (SPARC) database. We fit the theoretical predictions of the rotation curves in conformal gravity with the SPARC data by using the Multi Start and Global Search methods. In the total expression of the tangential velocity we also include the effects of the baryonic matter, and the mass to luminosity ratio. Our results indicate that the simple solution of the Weyl geometric gravity can successfully account for the large variety of the rotation curves of the SPARC sample, and provide a satisfactory description of the particle dynamics in the galactic halos, without the need of introducing the elusive dark matter particle.