We discuss the determination of the linear power spectrum of dark matter fluctuations from measurements of the transmitted flux Ly-α Forest power spectrum. We show that at most scales probed by current measurements, the flux power spectrum is significantly affected by non-linear corrections to the linear dark matter power spectrum due to gravitational clustering. Inferring the linear dark matte...

There is mounting evidence from observations of long duration gamma ray bursts (GRBs), supernova remnants (SNR) and the supernova (SN) explosion 1987A, that SN explosions eject highly relativistic bipolar jets of plasmoids (cannonballs) of ordinary matter. The highly relativistic plasmoids sweep up the ambient matter in front of them, accelerate it to cosmic ray (CR) energies and disperse it al...

Shock waves driven in the intergalactic medium during the merging of galaxy clusters have been observed in X-ray imaging and spectroscopy. Fluid motions inferred from the shock strength and morphology can be compared to the cold dark matter (CDM) distribution inferred from gravitational lensing. A detailed reconstruction of the CDM kinematics, however, must take into account the nontrivial resp...

Shock waves driven in the intergalactic medium during the merging of galaxy clusters have been observed in X-ray imaging and spectroscopy. Fluid motions inferred from the shock strength and morphology can be compared to the cold dark matter (CDM) distribution inferred from gravitational lensing. A detailed reconstruction of the CDM kinematics, however, must take into account the nontrivial resp...

High–resolution hydrodynamics simulations of the Lyα forest in cold dark matter dominated cosmologies appear to predict line widths that are substantially narrower than those observed. Here we point out that Compton heating of the intergalactic gas by the hard X–ray background (XRB), an effect neglected in all previous investigations, may help to resolve this discrepancy. The rate of gain in th...

High–resolution hydrodynamics simulations of the Lyα forest in cold dark matter dominated cosmologies appear to predict line–widths that are substantially narrower than those observed. Here we point out that Compton heating of the intergalactic gas by the hard X–ray background (XRB), an effect neglected in all previous investigations, may help to resolve this discrepancy. The rate of gain in th...

The growth of galaxies is driven by two processes: mergers with other galaxies and smooth accretion of intergalactic gas. The relative share of this two processes depends on the environment (rich cluster or field), and determines the morphological evolution of the galaxy. In this work we focus on the properties of accretion onto galaxies. Through numerical simulations we investigate the geometr...

Dark Matter annihilations after recombination and during the epoch of structure formation deposit energy in the primordial intergalactic medium, producing reionization and heating. We investigate the constraints that are imposed by the observed optical depth of the Universe and the measured temperature of the intergalactic gas. We find that the bounds are significant, and have the power to rule...

We argue that any violent galactic winds following early epoch of star bursts would significantly weaken the potentials of galaxies, and leave lasting signatures such as a lowered dark halo density and preferentially radial/escaping orbits for halo tracers such as globular clusters. A galaxy is disintegrated if more than half of its dynamical mass is blown off. The presence of dense halos in ga...