  High resolution Halpha rotation curves are presented for five low surface
brightness galaxies. These Halpha rotation curves have shapes different from
those previously derived from HI observations, probably because of the higher
spatial resolution of the Halpha observations. The Halpha rotation curves rise
more steeply in the inner parts than the HI rotation curves and reach a flat
part beyond about two disk scale lengths. With radii expressed in optical disk
scale lengths, the rotation curves of the low surface brightness galaxies
presented here and those of HSB galaxies have almost identical shapes. Mass
modeling shows that the contribution of the stellar component to the rotation
curves may be scaled to explain most of the inner parts of the rotation curves,
albeit with high stellar mass-to-light ratios. On the other hand, well fitting
mass models can also be obtained with lower contributions of the stellar disk.
These observations suggest that the luminous mass density and the total mass
density are coupled in the inner parts of these galaxies.
