The simulation parameters
can be broken down into intrinsic, and orbital
types.
The intrinsic parameters are
the relative masses of the galaxies, the relative scale lengths (size),
the form of the mass distribution and the rotation speeds. For all
the simulations a Hernquist potential was chosen for the satellite galaxy
and a Dehnen model which is essentially a rotating Hernquist potential
flattend so that the small to large axis ratio is 0.7 is used for the primary
galaxy.
In order to have the simulations
cover the most realtistic parameters the relative scale size and mass for
all the possible pairs of elliptical galaxies from a sample was plotted
below.
The dashed lines mark contours
of constant density centers. The merger pairs in the lower left hand
corner consist of very small galaxies falling into very large galaxies.
The chance of of being able to detect such a merger is very low and this
possibility is therefore not modeled. The merger pairs in the upper right
hand corner consist of galaxies close to equal in size merging. Such occurances
are known as major mergers and fall outside the range of these simulations.
The nine diamonds in the square show the values of mass and scale radius
which were chosen for the simulations.
The satellite's orbital parameter
values are chosen too maximize coverage of the possible parameter space
using only a few simulations. The relevant parameters are the eccentricity
of the satellite orbit, the inclination of the orbit with respect to the
rotation plane of the primary and the initial distance between the two
galaxies. This distance should preferably be very large, but time constraints
limit the initial separation to 2.5 half mass radii. Testing shows that
this does not significantly effect the results. Orbital inclinations of
0, 30 and 60 degrees were chosen to span the range of possible mergers.
Likewise eccentricities of 0 and 0.6 were chosen.
The above choices result in
a total of 54 simulations being performed.
 |
 |