  Galaxies and galaxy clusters are observed to have a rather non-trivial radial
behaviour. The observations show that the radial profiles change from one
power-law profile near the centre to another power-law profile in the outer
region. We present a simple explanation for this complex behaviour by finding
the analytical solutions to the governing hydrodynamic equations. We see that
the origin of this complexity is the collisional nature of the baryonic plasma,
possibly related to a turbulence-enhanced viscosity.
