Two examples of clusters dynamical cusps: A496 and Sersic40/6.

Velocity dispersions and virial masses are presented for the clusters Sersic40/6 and A496, based on previously published and recently obtained data. The authors discuss the presence in both clusters of a tight group of faint members surrounding the central galaxies, forming density cusps. However, in contrast to other examples of clusters, as in A2029, the core galaxies have much smaller dispersions than the overall clusters, with values similar to the cD halo dispersion. Thus, assuming that these cores are bound to the central galaxies, the authors can derive an estimate of the dynamical masses in the cores, which will include any dark matter in the immediate vicinity of the cD's.