Several effects can contribute to the transverse broadening of the velocity profile. Individual stars themselves rotate as they orbit, so the side approaching will be blueshifted and the side moving away will be redshifted. Stars also have random (as well as orbital) motion around the galaxy, meaning any individual star may depart significantly from the rest relative to its neighbours in the rotation curve. In spiral galaxies this random motion is small compared to the low-eccentricity orbital motion, but this is not true for an elliptical galaxy. Molecular-scale Doppler broadening will also contribute.