The distribution and kinematics of early high-sigma peaks in present-day haloes: implications for rare objects and old stellar populations
Abstract
We show that the hierarchical assembly of cold dark matter haloes preserves the memory of the initial conditions. Using N-body cosmological simulations, we demonstrate that the spatial distribution and kinematics of objects that formed within early galactic haloes (old stars, satellite galaxies, globular clusters, black holes etc.) depends only on the rarity of the peak in which they formed. Matter from the rarer peaks of the primordial density field ends up more concentrated and falling off more steeply with radius compared to the overall mass distribution, it has a lower velocity dispersion, moves on more radial orbits and has a more elongated shape. Population II stars that form in cold dark matter dominated proto-galaxies that were 2.5 sigma peaks end up with a half light radius of 16.9 kpc, falling off as r^{-3.5} with an anisotropy varying from isotropic in the inner halo to nearly radial at the halo edge. This agrees well with the kinematics of halo red giant stars recently observed by Battaglia et al. (2005).Keywords
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