  We study the effects of mass and force resolution on the density profiles of
galaxy-size Cold Dark Matter (CDM) halos in a flat, low-density cosmological
model with vacuum energy. We show thatalthough increasing the mass and force
resolution allows us to probe deeper into the inner halo regions, it does not
lead to steeper inner density profiles. Instead, the halo profiles converge at
scales larger than four times the formal resolution or the radius containing
more than 200 particles, whichever is larger. In the simulations presented in
this paper, we are able to probe density profile of a relaxed isolated
galaxy-size halo at scales r=(0.005-1)r_vir. We find that the density
distribution can be well approximated by the profile suggested by Moore etal
(1998): rho= x^{-1.5}(1+x^{1.5})^-1, where x=r/r_s and r_s is the
characteristic radius. The analytical profile proposed by Navarro et al. (1996)
rho= x^{-1}(1+x)^-2, also provides a good fit, with the same relative errors of
about 10% for radii larger than 1% of the virial radius. Both analytical
profiles fit equally well because for high-concentration galaxy-size halos the
differences between these profiles become significant only at scales well below
0.01r_vir. We also find that halos of similar mass may have somewhat different
parameters (characteristic radius, maximum rotation velocity, etc.) and shapes
of their density profiles. We associate this scatter in properties with
differences in halo merger histories and the amount of substructure present in
the analyzed halos.
