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In the cold dark matter model of structure formation, galaxies are assembled hierarchically from mergers and the accretion of subclumps. This process is expected to leave residual substructure in the Galactic dark halo, including partially…
By analysing the Chandra and XMM-Newton archived data of the nearby galaxy cluster Abell 3158, which was reported to possess a relatively regular, relaxed morphology in the X-ray band in previous works, we identify a bow edge-shaped…
A theoretical model framework of spherical symmetry is presented for a composite astrophysical system of two polytropic fluids coupled together by gravity to explore large-scale shocks and flow dynamics in clusters of galaxies or in…
Deep Chandra exposures of the hot galaxy cluster 1E0657-56 have revealed that the cluster is observed shortly after the first core-passage of a massive infalling subcluster, which is preceded by a prominent bow shock with Mach number M~3.…
X-ray shocks and radio relics detected in the cluster outskirts are commonly interpreted as shocks induced by mergers of sub-clumps. We study the properties of merger shocks in merging galaxy clusters, using a set of cosmological…
We present numerical simulations of the passage of clumpy gas through a galactic spiral shock, the subsequent formation of giant molecular clouds (GMCs) and the triggering of star formation. The spiral shock forms dense clouds while…
Cooling flows, cluster mergers and motions of galaxies through the cluster gas with supersonic and sonic velocities must lead to large scale motions of the intracluster medium (ICM). A high-resolution numerical simulation of X-ray cluster…
The hot X-ray emitting plasma in galaxy clusters is predicted to have turbulent motions which can contribute around ten percent of the cluster's central energy density. We report deep Chandra X-ray Observatory observations of the Coma…
Determining the structure of galaxy clusters is essential for an understanding of large scale structure in the universe, and may hold important clues to the identity and nature of dark matter particles. Moreover, the core dark matter…
For the past forty years the search for dark matter has been one of the primary foci of astrophysics, although there has yet to be any direct evidence for its existence (Porter et al. 2011). Indirect evidence for the existence of dark…
It appears that the majority of rapidly-, well-localized gamma-ray bursts with undetected, or dark, optical afterglows, or `dark bursts' for short, occur in clouds of size R > 10L_{49}^{1/2} pc and mass M > 3x10^5L_{49} M_{sun}, where L is…
With the success of the Chandra and XMM missions and the maturation of gravitational lensing techniques, powerful constraints on the orbital structure of cluster dark matter halos are possible. I show that the X-ray emissivity and mass of a…
The nonthermal radiation observed from a handfull of clusters of Galaxies is the proof that particle acceleration occurs in the intracluster medium. It is often believed that shock surfaces associated with either mergers of clusters of…
We have performed a series of N-body experiments on Connection Machine-5 in order to simulate the formation of galaxy clusters gravitationally dominated by a massive dark background. In accordance with previous authors we find an extremely…
Dark plasma is an intriguing form of self-interacting dark matter with an effective fluid-like behavior, which is well motivated by various theoretical particle physics models. We aim to find an explanation for an isolated mass clump in the…
Astrophysical gases such as the interstellar-, circumgalactic- or intracluster-medium are commonly multiphase, which poses the question of the structure of these systems. While there are many known processes leading to fragmentation of cold…
High-resolution Chandra images of several clusters of galaxies reveal sharp, edge-like discontinuities in their gas density. The gas temperature is higher in front of the edge where the density is low, corresponding to approximately…
Type 1 active galactic nuclei display broad emission lines, regarded as arising from photoionized gas moving in the gravitational potential of a supermassive black hole. The origin of this broad-line region gas is unresolved so far,…
Recent observations and stellar dynamics simulations suggest that thousand solar mass black holes can form in compact massive young star clusters. Any such clusters in the bulge of their host galaxy will spiral to the center within a few…
It is generally argued that most clusters of galaxies host cooling flows in which radiative cooling in the centre causes a slow inflow. However, recent observations by Chandra and XMM conflict with the predicted cooling flow rates. It has…