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11 papers found.
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The spatial distribution of galactic satellites in the Λ cold dark matter cosmology

We investigate the spatial distribution of galactic satellites in high-resolution simulations of structure formation in the Λ cold dark matter (ΛCDM) model: the Aquarius dark matter simulations of individual haloes and the Millennium-II simulation of a large cosmological volume. To relate the simulations to observations of the Milky Way we use two alternative models to populate...

A systemic study of 14 southern infrared dark clouds with N2H+, HNC, HCO+ and HCN lines

We studied 14 southern infrared dark clouds (IRDCs) using data taken from the Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey and the GLIMPSE and MIPSGAL mid-infrared surveys of the inner Galaxy. The physical and chemical characteristics of the 14 IRDCs were investigated using N2H+(1–0), HNC(1–0), HCO+(1–0) and HCN(1–0) molecular lines. We found that the 14 IRDCs are in...

Are mergers responsible for universal halo properties?

N-body simulations of cold dark matter (CDM) have shown that, in this hierarchical structure formation model, dark matter halo properties, such as the density profile, the phase-space density profile, the distribution of axial ratio, the distribution of spin parameter and the distribution of internal specific angular momentum, follow ‘universal’ laws or distributions. Here, we...

Discreteness effects in simulations of hot/warm dark matter

In hot/warm dark matter (HDM/WDM) universes the density fluctuations at early times contain very little power below a characteristic wavelength related inversely to the particle mass. We study how discreteness noise influences the growth of non-linear structures smaller than this coherence scale in N-body simulations of cosmic structure formation. It has been known for 20 yr that...

Substructure lensing: effects of galaxies, globular clusters and satellite streams

Lensing flux-ratio anomalies have been frequently observed and taken as evidence for the presence of abundant dark matter substructures in lensing galaxies, as predicted by the cold dark matter (CDM) model of cosmogony. In previous work, we examined the cusp–caustic relations of the multiple images of background quasars lensed by galaxy-scale dark matter haloes, using a suite of...

The haloes of bright satellite galaxies in a warm dark matter universe

High-resolution N-body simulations of galactic cold dark matter haloes indicate that we should expect to find a few satellite galaxies around the Milky Way whose haloes have a maximum circular velocity in excess of 40 km s−1. Yet, with the exception of the Magellanic Clouds and the Sagittarius dwarf, which likely reside in subhaloes with significantly larger velocities than this...

The dependence of galaxy formation on cosmological parameters: can we distinguish between the WMAP1 and WMAP3 parameter sets?

Jie Wang Gabriella De Lucia Manfred G. Kitzbichler Simon D. M. White Max-Planck-Institut fur Astrophysik Karl-Schwarzschild-Str. D- Garching Germany A B S T R A C T We combine N-body simulations of

Secondary infall and the pseudo-phase-space density profiles of cold dark matter haloes

We use N-body simulations to investigate the radial dependence of the density, ρ, and velocity dispersion, σ, in cold dark matter (CDM) haloes. In particular, we explore how closely Q≡ρ/σ3, a surrogate measure of the phase-space density, follows a power law in radius. Our study extends earlier work by considering, in addition to spherically averaged profiles, local Q estimates...

The diversity and similarity of simulated cold dark matter haloes

We study the mass, velocity dispersion and anisotropy profiles of Λ cold dark matter (ΛCDM) haloes using a suite of N-body simulations of unprecedented numerical resolution. The Aquarius Project follows the formation of six different galaxy-sized haloes simulated several times at varying numerical resolution, allowing numerical convergence to be assessed directly. The highest...

Phase-space structure in the local dark matter distribution and its signature in direct detection experiments

We study predictions for dark matter (DM) phase-space structure near the Sun based on high-resolution simulations of six galaxy haloes taken from the Aquarius project. The local DM density distribution is predicted to be remarkably smooth; the density at the Sun differs from the mean over a best-fitting ellipsoidal equidensity contour by less than 15 per cent at the 99.9 per cent...

Effects of dark matter substructures on gravitational lensing: results from the Aquarius simulations

We use the high-resolution Aquarius simulations of the formation of Milky Way-sized haloes in the Λ cold dark matter cosmology to study the effects of dark matter substructures on gravitational lensing. Each halo is resolved with ∼108 particles (at a mass resolution mp∼ 103 to 104 h−1 M⊙) within its virial radius. Subhaloes with masses msub≳ 105 h−1 M⊙ are well resolved, an...