HI in the Milky Way - Selected problems illustrated by the Leiden/Dwingeloo survey

Some of the principal problems which can be confronted with HI observations of our Galaxy are illustrated here by a selection of maps showing the disposition on the sky of HI emitting in particular velocity ranges. The data are from the new Leiden/Dwingeloo survey of the entire sky north of delta greater than or equal to -30 degrees, which has occupied the 25-meter radio telescope of the Netherlands Foundation for Research in Astronomy for a period of five years. The tendency of the general gas/dust correlation to involve some HI structures with quite anomalous velocities is illustrated by comparing some lambda 21-cm data taken on a finer grid using the Arecibo 1000-foot telescope with IRAS data in the 100-micron band.