Recent observations of high velocity clouds (HVCs) have revealed compression fronts and tail shaped features of HI suggesting that they are interacting with an external medium. We perform 3-D hydrodynamical simulations of HVCs moving through a diffuse hot gaseous component, investigating the behaviour of both extra-galactic dark matter dominated HVCs and nearby pure gas clouds that may be accre...

Gunn-Peterson tests suggest that the Universe was re-ionized after the _tazldard recombination epoch. We present a systematic treatment of the ionization process by deriving the Boltzmann equations appropriate to this regime. A compact solution for the photon spectrum is found in terms of the ionization ratio. These equations are then solved numerically for the Decaying Dark Matter scenario, wh...

This paper reviews the field of gamma-ray astronomy and describes future experiments and prospects for advances in fundamental physics and high-energy astrophysics through gamma-ray measurements. We concentrate on recent progress in the understanding of active galaxies, and the use of these sources as probes of intergalactic space. We also describe prospects for future experiments in a number o...

While gravitation sustains the on-going evolution of the cosmos, it is magnetism that breaks gravity’s symmetry and that provides the pathway to the non-thermal Universe. By enabling processes such as anisotropic pressure support, particle acceleration, and jet collimation, magnetism has for billions of years regulated the feedback vital for returning matter to the interstellar and intergalacti...

Recent studies have considered modifications to the standard weakly interacting massive particle scenario in which the pair annihilation cross section (times relative velocity v) is enhanced by a factor 1/upsilon to approximately 10(-3) in the Galaxy, enough to explain several puzzling Galactic radiation signals. We show that in these scenarios a burst of weakly interacting massive particle ann...

A. Introductionn.-So far oiliy interactions of cosmic rays with terrestrial matter have been investigated. If cosmic rays are present in interstellar and intergalactic space, they produce physical changes on extraterrestrial objects also. The question therefore arises if such changes are observable. The following considerations make it probable that this question is to be answered in the affirm...

We present the first measurements of the X-ray size-temperature (ST) relation in intermediate redshift galaxy clusters. We interpret the local ST relation in terms of underlying scaling relations in the cluster dark matter properties, and then we use standard models for the redshift evolution of those dark matter properties to argue that the ST relation does not evolve with redshift. We then us...

We investigate the impact of the intracluster medium on the weak-lensing shear power spectrum. The shear power spectrum depends on the total mass power spectrum. With the halo model, we find that the baryon power spectrum is significantly lower than the dark matter power spectrum on scales well below the linear scale. The effect on the shear power spectrum is much less pronounced. Nevertheless,...

Many clusters of galaxies contain an appreciable amount of hot gas, the intracluster medium. As a consequence, gas will be stripped from galaxies that move through the inter cluster medium, if the ram pressure exceeds the internal gravitational force. We study the interaction between the intracluster medium and an extended gas component of dwarf galaxies confined by a surrounding cold dark matt...