Dynamical friction of radio galaxies in galaxy clusters

The distribution of luminous radio galaxies in galaxy clusters has been observed to be concentrated in the inner region. We consider the role of dynamical friction of massive galaxies (M similar to 10(12.5) M(circle dot)), assuming them to be hosts of luminous radio galaxies, and show that beginning with a Navarro-Frenk-White density profile of a cluster of mass M(c1) similar to 10(15) M(circle dot) of concentration c similar to 25, as observed , in a time-scale of t similar to 3-5 Gyr.