Galactic rotation curves of spiral galaxies and dark matter in f(R,T) gravity theory

Abstract: Galactic rotation curve is a powerful indicator of the state of the gravitational field within a galaxy. The flatness of these curves indicates the presence of dark matter in galaxies and their clusters. In this paper, we focus on the possibility of explaining the rotation curves of spiral galaxies without postulating the existence of dark matter in the framework of $f(\mathcal{R},T)$ gravity, where the gravitational Lagrangian is written by an arbitrary function of $\mathcal{R}$, the Ricci scalar and of $T$, the trace of energy-momentum tensor $T_{\mu\nu}$. We derive the gravitational field equations in this gravity theory for the static spherically symmetric spacetime and solve the equations for metric coefficients using a specific model that has minimal coupling between matter and geometry. The orbital motion of a massive test particle moving in a stable circular orbit is considered and the behavior of its tangential velocity with the help of the considered model is studied. We compare the theoretical result predicted by the model with observations of a sample of nineteen galaxies by generating and fitting rotation curves for the test particle to check the viability of the model. It is observed that the model could almost successfully explain the galactic dynamics of these galaxies without the need of dark matter at large distances from the galactic center.