  We re-examine the disk-halo decompositions of the rotation curves of low
surface brightness (LSB) galaxies with V_max > 80 km/s, taking full account of
the effects of beam smearing. We show that the rotation curves of these LSB
galaxies are, contrary to previous claims, consistent with dark halos with
steep central cusps in their density distribution. In fact, the spatial
resolution of the data is not sufficient to put any meaningful constraints on
the density profiles of their dark halos, or on cosmological parameters. This
has important implications for numerous claims made in the literature regarding
the halos of LSB galaxies, such as the self-similarity of their rotation
curves, and their inconsistency with certain cosmological models or with cold
dark matter altogether. Only in one case is the data of sufficient spatial
resolution to obtain reliable constraints on the slope of the central density
distribution of the dark matter halo. For this single case, we find a central
density cusp with a slope 0.55 < alpha < 1.26 at the 99.73 percent confidence
levels. This contrasts strongly with the results for two dwarf galaxies (V_max
< 70 km/s) that we analyze, which yield alpha < 0.5 at the same level of
confidence. This possibly suggests that halos with constant density cores are
restricted to low-mass systems. We show that violent outflows of baryonic
matter by supernovae feedback can reproduce this mass-dependence of halo cusp
slopes.
