We present results of a study of the formation and evolution of the dark matter (DM) halos in a COBE-normalized spatially flat ΛCDM model (Ω0 = 1 − ΩΛ = 0.3; h = 0.7). The dynamics of 256 3 DM particles is followed numerically in a box of 60h Mpc with the dynamic range of 32, 000 in spatial resolution. The high resolution of the simulation allows us to examine evolution of both isolated and sat...

From the analysis of high–quality optical rotation curves of 9 low–luminosity disk galaxies, we find that the properties of the dark halos around these objects are inconsistent with the halo density profile of the halos emerging in high resolution Cold Dark Matter N-body simulations. Dark halos around galaxies are almost constant density spheres, very different from the characteristic CDM ρ(r) ...

Divergent-light halos are produced when light from nearby light sources is scattered by ice crystals in the atmosphere. We present a theory of divergent-light halos leading to an improved algorithm for the simulation of such halos. Contrary to the algorithm that we presented earlier for simulating such halos, the new algorithm includes a mathematically rigorous weighting of the events. The comp...

Recent high-resolution simulations of the formation of dark-matter halos have shown that the distribution of subhalos is scale-free, in the sense that if scaled by the velocity dispersion of the parent halo, the subhalo velocity distribution function of galaxy-sized and cluster-sized halos are identical. For clustersized halos, simulation results agreed well with observations. Simulations, howe...

Aims. We recently performed a study of a sample of relaxed, cooling core galaxy clusters with deep Very Large Array observations at 1.4 GHz. We find that in the central regions of A1835, A2029, and Ophiuchus the dominant radio galaxy is surrounded by a diffuse low-brightness radio emission that takes the form of a mini-halo. Here we present the results of the analysis of the extended diffuse ra...

We study properties of dark matter halos at high redshifts z = 2−10 for a vast range of masses with the emphasis on dwarf halos with masses 10−10hM⊙. We find that the density profiles of relaxed dwarf halos are well fitted by the NFW profile and do not have cores. We compute the halo mass function and the halo spin parameter distribution and find that the former is very well reproduced by the S...

I review what we currently do and do not know about the masses of disk galaxies and their dark matter halos. The prognosis for disks is good: the asymptotic rotation velocity provides a good indicator of total disk mass. The prognosis for halos is bad: cuspy halos provide a poor description of the data, and the total mass of individual dark matter halos remains ill-constrained.

We describe a general framework for systematically treating halos that are due to refraction in preferentially oriented ice wedges, and we construct an atlas of such halos. Initially we are constrained neither by the interfacial angles nor the orientations of real ice crystals. Instead we consider "all possible" refraction halos. We therefore make no assumption regarding the wedge angle, and on...