Systematics of H II rotation curves

Systematic rotational properties of field spiral galaxies are presented as a function of Hubble type and of luminosity. Within a Hubble type, radius, nuclear velocity gradient, rotation velocity, mass, and mass density increase with luminosity, while M/L is constant. At fixed luminosity, V(max), mass, density, and M/L decrease from Sa through Sc. These variations are so systematic that it is possible to display them on a single diagram.