Sersic galaxy with Sersic halo models of early-type galaxies: a tool for
  N-body simulations
  We present spherical, non-rotating, isotropic models of early-type galaxies
with stellar and dark-matter components both described by deprojected Sersic
density profiles, and prove that they represent physically admissible stable
systems. Using empirical correlations and recent results of N-body simulations,
all the free parameters of the models are expressed as functions of one single
quantity: the total (B-band) luminosity of the stellar component.
  We analyze how to perform discrete N-body realizations of Sersic models. To
this end, an optimal smoothing length is derived, defined as the softening
parameter minimizing the error on the gravitational potential for the
deprojected Sersic model. It is shown to depend on the Sersic index $n$ and on
the number of particles of the N-body realization.
  A software code allowing the computations of the relevant quantities of one-
and two-component Sersic models is provided. Both the code and the results of
the present work are primarily intended as tools to perform N-body simulations
of early-type galaxies, where the structural non-homology of these systems
(i.e. the variation of the shape parameter along the galaxy sequence) might be
taken into account.
