Distribution and kinematics of neutral hydrogen in the spiral galaxy M81

In this investigation we analyze observations of the early type spiral galaxy M8l (NGC 3031) made with the Westerbork Synthesis Radio Telescope in the 2l-cm line of neutral atomic hydrogen. The angular resolution is 24"x26" which, at a distance of 3.25 Mpc, corresponds to a linear resolution in the plane of the sky of 380x400 pc, or 400x800 pc in the plane of the galaxy. We confine ourselves to an area of 33'x37'. A velocity range from -300 km/s to +320 km/s is covered at a resolution of 27 km/s. ... Zie: Summary