ON THE ORIGIN OF CUSPS IN DARK-MATTER HALOS

Observed cusps with density profiles p proportional to r(-1) or shallo wer in the central regions of galaxies cannot be reproduced in the sta ndard cold dark matter picture of hierarchical clustering. Previous cl aims to the contrary were based on simulations with relatively few par ticles and substantial softening. We present simulations with particle numbers 1 order of magnitude higher and essentially no softening, and we show that typical central density profiles are clearly steeper tha n p proportional to r(-1). The observed shallower profiles may have fo rmed through the smoothing effect of the spiral-in of central black ho les in previous merger phases. In addition, we confirm the presence of a temperature inversion in the inner 5 kpc of massive galactic halos and illustrate its formation as a natural result of the merging of une qual progenitors.