Example 5: Plummer model with circular orbits, self-gravity

This is the same scenario as the previous example, except that now the system evolves under its own self-gravity rather than an external potential. The instructions are the same as previously, namely

mkdir snap python makeIC.py bash run.sh

Note that it doesn't matter if SWIFT was configured/compiled with an external potential, as it is disabled at runtime in the run.sh script.

To visualize the results, as before run

python ../visualize.py snap/snapshot_*.hdf5 -shift 10 -lim 5 -nbins 800 -frsp 0.4 -interp bilinear -fps 50 --savefilm

Plot the Velocity Dispersion

To see how the dispersion of the different components of the velocity evolves with time, the script dispersion_profile.py is provided. By default, when given a set of snapshots, the script will produce two plots corresponding to the radial and tangential components of the velocty dispersion against radius, for each snapshot. It achieves this by placing the particles in radial bins, projecting their velocities onto r and t components and computing the variance. Assuming default parameters were used, the following produces a comprehensive plot of the time-evolution:

python dispersion_profile.py snap/snapshot_0*00.hdf5 -Rmax 7

To save the plot, append --saveplot to the command.

Plot the Density profile

To quantify how the initially spherical, Plummer mass distribution evolves, the density_profile.py script is used to plot the mass density against radius, for a set of snapshot files (as above). To use the script, run e.g.

python density_profile.py snap/snapshot_0*00.hdf5

To save the plot, append --saveplot to the command.