MARSEILLES OBSERVATORY H-ALPHA SURVEY OF THE SOUTHERN GALACTIC PLANE AND MAGELLANIC CLOUDS

The ionised gas regions, which are the main tracers of the spiral arms , can be used for the study and determination of the spiral structure of our Galaxy. Towards this goal, the Marseille Observatory elaborated and developed an instrument, using a scanning Fabry-Perot interferome ter, particularly suited for the observation of extended objects. A su rvey of the southern Galactic plane then started at the beginning of 1 990. The major instrumental aim is to obtain spectral information, and therefore the ionised gas kinematics, in each pixel of the observed f ields. Already 300 fields of 38' x 38' have been observed in H alpha w ith a spatial resolution of 9 '' x 9 '', covering almost the entire fo urth quadrant of the Galactic plane, and numerous discrete HII regions have been detected! as well as diffuse emission which is widely distr ibuted. Also, the Magellanic Clouds have been studied using the same i nstrument.