I develop a model for the abundance and spatial distribution of dark matter subclumps. The model shows that subclumps of massive parent halos formed at earlier times than subclumps of the same mass in lower mass parents; equivalently, halos in dense regions at a given time formed earlier than halos of the same mass in less dense regions. This may provide the basis for interpreting recent observ...

We present new results on the angular momentum evolution of dark matter halos. Halos, from N-body simulations, are classified according to their mass growth histories into two categories: the accretion category contains halos whose mass has varied continuously and smoothly, while the merger category contains halos which have undergone sudden and significant mass variations (greater than 1/3 of ...

We use numerical simulations to investigate the importance of HD formation and cooling on the first generation of metal-free stars in a ΛCDM cosmology. We have implemented and tested nonequilibrium HD chemistry in an adaptive mesh refinement simulation code and applied it to two situations. (1) It is first applied to the formation of 10 − 10 M⊙ halos which form in the absence of any ionizing so...

We show that, in the halo model of large-scale structure formation, the difference between the Fourier and the DWT (discrete wavelet transform) power spectra provides a statistical measurement of the halos. This statistical quantity is free from parameters related to the shape of the mass profile and the identification scheme of halos. That is, the statistical measurement is invariant in the se...

The gravitational lensing properties of cosmological halos depend upon the mass distribution within each halo. The description of halos as nonsingular, truncated isothermal spheres, a particular solution of the isothermal Lane-Emden equation (suitably modified for Λ 6= 0), has proved to be a useful approximation for the halos which form from realistic initial conditions in a CDM universe. The n...

We use N-body simulations to investigate the structure of dark halos in the standard Cold Dark Matter cosmogony. Halos are excised from simulations of cosmologically representative regions and are resimulated individually at high resolution. We study objects with masses ranging from those of dwarf galaxy halos to those of rich galaxy clusters. The spherically averaged density prooles of all our...

Hierarchical Cold Dark Matter (CDM) models predict that Milky Way sized halos contain several hundred dense low-mass dark matter satellites (the substructure), an order of magnitude more than the number of observed satellites in the Local Group. If the CDM paradigm is correct, this prediction implies that the Milky Way and Andromeda are filled with numerous dark halos. To understand why these h...

Rotation curves place important constraints on the radial mass distribution of dark matter halos, ρ(r). At large radii, rotation curves tend to become asymptotically flat. For ρ(r) ∝ r, this implies α ≈ −2, which persists as far out as can be measured. At small radii, the data strongly prefer dark matter halos with constant density cores (α ≈ 0) over the cuspy halos (α ≤ −1) predicted by cosmol...

Aims. We revisit the study of the mass functions and the bias of dark matter halos. Methods. Focusing on the limit of rare massive halos, we point out that exact analytical results can be obtained for the large-mass tail of the halo mass function. This is most easily seen from a steepest-descent approach, that becomes asymptotically exact for rare events. We also revisit the traditional derivat...

We present a new method for calculating the merger history of matter halos in hierarchical clustering cosmologies. The linear density field is smoothed on a range of scales, these are then ordered in decreasing density and a merger tree constructed. The method is similar in many respects to the block model of Cole & Kaiser but has a number of advantages: (i) it retains information about the spa...