# GALIC – Code

The GALIC code is a publicly available
program that implements a new iterative method for the
construction of N-body galaxy models in collisionless
equilibrium. The method uses elements of Schwarzschild’s
technique and of the made-to-measure method, but is based on a
different principle. Starting with some initial assignment of
particle velocities, the difference of the time-averaged density
response produced by the particle orbits with respect to the
initial density configuration is characterized through a merit
function, and a stationary solution of the collisionless
Boltzmann equation is found by minimizing this merit function
directly by iteratively adjusting the initial velocities.
Because the distribution function is in general not unique for a
given density structure, the merit function is augmented with
additional constraints that single out a desired target
solution. The velocity adjustment is carried out with a
stochastic process in which new velocities are randomly drawn
from an approximate solution of the distribution function, but
are kept only when they improve the fit. The method converges
rapidly and is flexible enough to allow the construction of
solutions with third integrals of motion, including disc
galaxies in which radial and vertical dispersions are different.

The method has been developed by Denis
Yurin as part of this PhD thesis supervised by Volker
Springel. The code can be downloaded as

**galic.tar.gz**
(version 1.0)

which contains the source code as well
as a README file with instructions for building and running the
code. We note that the code is parallelized for distributed
memory based on MPI.

The principal reference for the method
and the code is the paper:

**An iterative method for the
construction of N-body galaxy models in collisionless
equilibrium**

Yurin D., Springel V. (2014)

Monthly Notices of the Royal Astronomical Society, 444,
62 [ADS]