Potential--density pairs for spherical galaxies and bulges: the influence of scalar fields

A family of potential--density pairs has been found for spherical halos and bulges of galaxies in the Newtonian limit of scalar--tensor theories of gravity. The scalar field is described by a Klein--Gordon equation with a source that is coupled to the standard Poisson equation of Newtonian gravity. The net gravitational force is given by two contributions: the standard Newtonian potential plus a term stemming from massive scalar fields. General solutions have been found for spherical systems. In particular, we compute potential--density pairs of spherical galactic systems, and some other astrophysical quantities that are relevant to generating initial conditions for spherical galaxy simulations.