## Rotationally symmetric (thin) structures: Keplerian disks

The KEPLER command re-aligns in velocity the spectra as a function of radius (distance from the rotation center), by correcting from the projection effect and radial velocity law. This allows to stack spectra coming from the same radius, and thus to derive radial profiles.

The result is a Position-Velocity image, and can be displayed conveniently with the SHOW KEPLER command.

The KEPLER command assumes by default that the velocity law is Keplerian. However, arbitrary analytic laws can be used (see KEPLER /VELOCITY, so that the tool can also be used for example for spectral lines in galaxies.