L. Gao, J. F. Navarro, C. S. Frenk, A. Jenkins, V. Springel, S. D. M. White
[abridged] We introduce the Phoenix Project, a set of LCDM simulations of the
dark matter component of nine rich galaxy clusters. Each cluster is simulated
at least at two different numerical resolutions. For eight of them, the highest
resolution corresponds to ~1.3e8 particles within the virial radius, while for
one this number is over one billion. Because of their recent assembly, these
cluster haloes are significantly less relaxed than galaxy haloes, leading to
decreased regularity, increased halo-to-halo variations, and systematic
differences in concentration and substructure fraction. All density profiles
steepen gradually from the centre outwards, but there is considerable scatter
in the dependence of logarithmic slope, gamma on radius. At the innermost
convergence radius, r_conv ~3 kpc/h (~ 0.2% of the virial radius) the mean and
rms scatter is gamma=1.05+-0.19 for the nine haloes. As for galaxy haloes,
there is little indication of an approach to an asymptotic inner power law. For
individual clusters, strongly aspherical mass distributions can produce
projected surface density variations at given radius spanning up to a factor of
three, depending on projection direction. This may in part explain the high
apparent concentration of some observed strong-lensing clusters. The shape of
the surface density profile, gamma_p(R) depends only weakly on projection
direction, however, and is quite well approximated in the inner regions by the
NFW formula. Substructure in the Phoenix haloes is slightly more abundant,
especially in the inner regions, than in the galaxy haloes of the Aquarius
Project. The subhalo mass function is also steeper: dN/dM \propto M^{-1.98} in
the range 1e-6View original: http://arxiv.org/abs/1201.1940
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