A thick-disk galaxy model and simulations of equal-mass galaxy pair
  collisions
  We implement a numerical model reported in the literature to simulate the
evolution of a galaxy composed of four matter components, such as: a
dark-matter halo; a rotating disk of stars; a spherical bulge of stars and a
ring of molecular gas. We show that the evolution of this galaxy model is
stable at least for 10 Gyr (Gyr=$10^{9}$ years). We characterize the resulting
configuration of this galaxy model by figures of the circular velocity and
angular momentum distribution; the tangential and radial components of the
velocity; the peak density evolution and the radial density profile.
Additionally, we calculate several models of equal-mass galaxy binary
collisions, such as: (i) frontal and (ii) oblique (with an impact parameter),
(iii) two models with initial conditions taken from a 2-body orbits and (iv) a
very close passage. To allow comparison with the galaxy model, we characterize
the dynamics of the collision models in an analogous way. Finally, we determine
the de Vaucouleurs fitting curves of the radial density profile, on a radial
scale of 0-100 kpc, for all the collision models irrespective of the
pre-collision trajectory. To study the radial mass density and radial surface
density profiles at a smaller radial scale, 0-20 kpc, we use a four-parameters
fitting curve.
