We describe cosmological simulation techniques and their application to studies of cosmic structure formation, with particular attention to recent hydrodynamic simulations of structure in the high redshift universe. Collisionless N-body simulations with Gaussian initial conditions produce a pattern of sheets, filaments, tunnels, and voids that resembles the observed large scale galaxy distribut...

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...

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 resolve this discrepancy. The rate of gain in thermal en...

We present a method to recover the shape and amplitude of the power spectrum of mass fluctuations, P (k), from observations of the high redshift Lyα forest. The method is motivated by the physical picture that has emerged from hydrodynamic cosmological simulations and related semi-analytic models, in which typical Lyα forest lines arise in a diffuse, continuous, fluctuating intergalactic medium...

We study the physical origin of the low-redshift Lyα forest in hydrodynamic simulations of four cosmological models, all variants of the cold dark matter scenario. Our most important conclusions are insensitive to the cosmological model, but they depend on our assumption that the UV background declines at low redshift in concert with the declining population of quasar sources. We find that the ...

We analyze the z = 2 Lyα and C IV forest along two adjacent lines-of-sight at high S/N and spectral resolution to assess the question of the origin of metals in the intergalactic medium. We find that the gas containing detectable amounts of metals (as seen in absorption by C IV) is less quiescent on scales of a few kpc than the gas without metals. Although it is difficult to discriminate unequi...

Lyα absorber correlations contain information about the underlying density distribution associated with a particular class of absorbers. As such, they provide an opportunity to independently measure the “bias” of the Lyman alpha forest, i.e. the relationship between H I column density and underlying dark matter density. In these proceedings we use hydrodynamic simulations to investigate whether...