Dark matter halos 469Figure 15.22.Profiles of halos B, C and D atz=1. The profiles of halos C and D were
offset downwards by factors of 10 and 100 for clarity. The full curves show simulated
profiles, while the dotted and chain curves show the NFW and Mooreet alfits, respectively.
The halo profiles in the simulations are plotted down to four formal resolutions. Each halo
had more than 200 particles inside the smallest plotted scale.
We found that the errors in the Mooreet alfits were systematically smaller
than those of the NFW fits, though the differences were not dramatic. The Moore
et alfit failed for halo D. It formally gave very small errors, but this was done for
a fit with an unreasonably small concentration (C=2). When we constrained
the approximation to have a concentration twice as large compared with the best
NFW fit, we were able to obtain a reasonable fit (this fit is shown in figure 15.22).
Nevertheless, the central part was fitted poorly in this case.
Our analysis therefore failed to determine which analytic profile provides a
better description of the density distribution in simulated halos. Despite the larger
number of particles per halo and lower concentrations of halos, the results are
still inconclusive. The Mooreet alprofile is a better fit to the profile of halo C;
the NFW profile is a better fit to the central part of halo D. Halo B represents