Circular velocity profiles of dark matter haloes

We use a high-resolution simulation of a galaxy-sized dark matter halo, published simulated data as well as four cluster-sized haloes from Fukushige, Kawai & Makino to study the inner halo structure in a Lambda cold dark matter cosmology. We find that the circular velocity curves are substantially better described by Stoehr et al. (SWTS) profiles than by Navarro, Frenk & White (NFW) or Moore et al. profiles. Our findings confirm that no asymptotic slope is reached and that the profiles are nearly universal, but not perfectly. The velocity profiles curve at a constant rate in log (r) over the full converged range in radii and the corresponding extrapolated density profiles reach a finite maximum density. We find that the claim of a strong discrepancy between the observed inner slopes of the density profiles of low surface brightness galaxies and their simulated counterparts on the grounds of currently available observations and simulations is unfounded. In addition, if the SWTS profile turns out to be a good description of the halo profile for the regions that cannot be probed with simulations of today, then even in these regions the agreement between simulations and observations is very reasonable.