Using N-body/hydrodynamic simulations, the influence of non-equipartition processes on the thermal and dynamical properties of cosmological baryonic gas is investigated. We focus on a possible departure from equilibrium between electrons, ions and neutral atoms in low temperature (10–10 K) and weakly ionized regions of the intergalactic medium. The simulations compute the energy exchanges betwe...

At the epoch of reionization, when the high-redshift intergalactic medium (IGM) is being enrichedwithmetals, the 63.2 mfine-structure line of O i is pumped by the 13008 soft UV background and introduces a spectral distortion in the cosmic microwave background (CMB). Here we use a toy model for the spatial distribution of neutral oxygen in which metal bubbles surround dark matter halos, and comp...

Early photoionization of the intergalactic medium is discussed in a nearly model-independent way, in order to investigate whether early structures corresponding to rare Gaussian peaks in a CDM model can photoionize the intergalactic medium sufficiently early to appreciably smooth out the microwave background fluctuations. We conclude that this is indeed possible for a broad range of CDM normali...

The Galaxy Evolution Explorer (GALEX) continues its surveys of the ultraviolet sky. GALEX surveys have supported the following galaxy evolution investigations: calibrating UV as a star formation rate tracer, using wide and deep surveys to measure star formation history, studying the evolution of dust extinction and metallicity, selecting and analyzing galaxies in transitory states, finding loca...

With a top-heavy initial stellar mass function for Population III stars, as recent simulations seem to suggest, we show that Pop III stars can, for the first time, reionize the universe at z ∼ 15 − 20 in the standard cold dark matter cosmological model. The physical reason rests in the positive feedback from Pop III star formation, made possible by a high X-ray background, which, in turn, is pr...

We present a precise estimate of the bulk virial scaling relation of halos formed via hierarchical clustering in an ensemble of simulated cold dark matter cosmologies. The result is insensitive to cosmological parameters, the presence of a trace, dissipationless gas component, and numerical resolution down to a limit of ∼ 1000 particles. The dark matter velocity dispersion scales with total mas...

Most of the baryons in the present-day universe are thought to reside in intergalactic space at temperatures of 10 K. X-ray emission from these baryons contributes a modest (∼10%) fraction of the ∼ 1 keV background whose prominence within the large-scale cosmic web depends on the amount of nongravitational energy injected into intergalactic space by supernovae and AGNs. Here we show that the vi...

Strong intergalactic shocks are a natural consequence of structure formation in the universe. These shocks are expected to deposit large fractions of their thermal energy in relativistic electrons (ξe ≃ 0.05 according to supernova remnant observations) and magnetic fields (ξB ≃ 0.01 according to cluster halo observations). We discuss the expected synchrotron emission from such shocks, and the o...