We present results of combined N-body and three-dimensional reionization calculations to determine the relationship between reionization history and local environment in a volume 1 Gpc h−1 across and a resolution of about 1 Mpc. We resolve the formation of about 2× 106 halos of mass greater than ∼ 10M⊙ at z = 0, allowing us to determine the relationship between halo mass and reionization epoch ...

In the standard paradigm, satellite galaxies are believed to be associated with the population of dark matter subhalos. The assumption usually made is that the relationship between satellite galaxies and sub-halos is similar to that between central galaxies and host halos. In this paper, we use the conditional stellar mass functions of satellite galaxies obtained from a large galaxy group catal...

The balance of evidence indicates that individual galaxies and groups or clusters of galaxies are embedded in enormous distributions of cold, weakly interacting dark matter. These dark matter “halos” provide the scaffolding for all luminous structures in the universe, and their properties comprise an essential part of the current cosmological model. I review the internal properties of dark matt...

Image flux ratio anomalies have been attributed to substructures within the gravitational lens and to small mass halos (M < ∼ 10 10 M⊙) in intergalactic space. In this paper, analytic calculations are presented that help in the understanding of how intergalactic halos affect magnification ratios. It is found that intergalactic halos can produce anomalies at a similar level to those that are obs...

We use a suite of high-resolution N-body simulations to study the properties, abundance and clustering of high mass halos at high redshift, including their mass assembly histories and mergers. We find that the analytic form which best fits the abundance of halos depends sensitively on the assumed definition of halo mass, with common definitions of halo mass differing by a factor of two for thes...

The first-generation stars in the ΛCDM universe are considered to have formed in dark halos with total masses in the range ∼ 10−10M⊙ at z ∼ 20−50. These stars expected to be very massive and in some cases they end their lives as the first supernovae (SNe). We explore the problem of whether star formation in low mass dark halos (6 10M⊙) was triggered or suppressed by the SN feedback from neighbo...

Using a high-resolution cosmologicalN -body simulation, we identify the ejected population of subhalos, which are halos at redshift z = 0 but were once contained in more massive ‘host’ halos at high redshifts. The fraction of the ejected subhalos in the total halo population of the same mass ranges from 9% to 4% for halo masses from ∼ 10 to ∼ 10 hM⊙. Most of the ejected subhalos are distributed...

Based on observed rotation curves of galaxies and theoretical simulations of dark matter halos, there are reasons for believing that at least three different types of dark matter halos exist in the Universe classified by their masses M and the inner slope of mass density −α : Population A (galaxies): 1010h−1M⊙ . M . 2× 1013h−1M⊙, α ≈ 2; Population B (cluster halos): M & 2× 10 13h−1M⊙, α ≈ 1.3; ...

Discrepancies have emerged between the predictions of standard cold dark matter (CDM) theory and observations of clustering on sub-galactic scales. Warm dark matter (WDM) is a simple modification of CDM in which the dark matter particles have initial velocities due either to their having decoupled as thermal relics, or having been formed via non-equilibrium decay. We investigate the nonlinear g...

Subsuns, Bottlinger's rings, and elliptical halos are simulated by the use of a Monte Carlo model; reflection of sunlight from almost horizontal ice crystals is assumed. Subsuns are circular or elliptical spots seen at the specular reflection point when one flies over cirrus or cirrostratus clouds. Bottlinger's rings are rare, almost elliptical rings centered about the subsun. Elliptical halos ...