2004PASP..116.1135H

This paper presents the radial velocity structure of the molecular hydrogen distribution in the Ring Nebula (NGC 6720). The structure was derived from the Doppler shift of the H₂v=1-0 S(1) line emission (2.122 µm, Δλ=0.02 µm), obtained using Fabry-Pérot spectroscopy. The kinematic results point to the fact that the molecular hydrogen emission is concentrated in an expanding hollow cylinder containing H₂clumps. In spite of the medium resolution of the observations, the kinematics of the H₂clumps in NGC 6720 are revealed, showing that they are distributed all over the ellipsoidal shell, with a wide range of values for their radial velocities and sizes.