21-cm line studies of spiral galaxies. II. The distribution and kinematics of neutral hydrogen in spiral galaxies of various morphological types.

Abstract

We have collected detailed 21-cm maps and associated velocity fields in order to study the relation between the dynamical and morphological properties of spiral galaxies. A description is given of the various deviations from axisymmetry in spirals as is evident from the velocity fields. A large number of spirals exhibit large-scale symmetric deviations, to be interpreted either as oval distortions or as kinematical warps. Most galaxies also have asymmetries, which are sometimes quite large. Motions associated with spiral arms are found only in studies with high resolution (radius/beam size larger than 15 or 20). Despite the complications due to the irregularities in the velocity fields, crude rotation curves can be derived. Most of them are flat enough to indicate that there is a large amount of high M/L material in the outer parts. The extent of a galaxy is not well determined and there is a large variety of H I sizes. The relation between dynamics and morphology of spiral galaxies could not be very well assessed in view of these complications. Associated Articles Part 1 Part 2