High-resolution rotation curves of low surface brightness galaxies

High-resolution H alpha rotation curves are presented for five low surface brightness galaxies. These H alpha rotation curves have shapes different from those previously derived from H I observations, probably because of the higher spatial resolution of the H alpha observations. The H alpha rotation curves rise more steeply in the inner parts than the H I rotation curves, and they reach a hat 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 the high surface brightness 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.