The two-component virial theorem and the physical properties of stellar systems

Motivated by present indirect evidence that galaxies are surrounded by dark matter halos, we investigate whether their physical properties can be desc ribed by a formulation of the virial theorem that explicitly takes into acc ount the gravitational potential term representing the interaction of the d ark halo with the baryonic or luminous component. Our analysis shows that t he application of such a "two-component virial theorem" not only accounts f or the scaling relations displayed by, in particular, elliptical galaxies, but also for the observed properties of all virialized stellar systems, ran ging from globular clusters to galaxy clusters.