Hα rotation curves:: The soft core question

We present high-resolution Halpha rotation curves of four late-type dwarf galaxies and two low surface brightness (LSB) galaxies, for which accurate H I rotation curves are available from the literature. Observations are carried out at Telescopio Nazionale Galileo. For LSB F583-1 an innovative dispersing element was used, the Volume Phase Holographic, with a dispersion of about 0.35 Angstrom pixel(-1). We find good agreement between the H data and the H I observations and conclude that the H I data for these galaxies suffer very little from beam smearing. We show that the optical rotation curves of these dark matter dominated galaxies are best fitted by the Burkert profile. In the centers of galaxies, where the N-body simulations predict cuspy cores and fast rising rotation curves, our data seem to be in better agreement with the presence of soft cores.