Constrained Simulations of the Real Universe. II. Observational Signatures of Intergalactic Gas in the Local Supercluster Region

We present results of gasdynamics+N-body constrained cosmological simulations of the Local Supercluster region (LSC; about 30h^-1Mpc around the Virgo cluster), which closely mimic the real universe within 100 Mpc, by imposing constraints from the MARK III catalog of galaxy peculiar velocities. The simulations are used to study the properties and possible observational signatures of intergalactic medium in the LSC region. We find that in agreement with previous unconstrained simulations, ~30% of the gas in this region is in the warm/hot phase at T~10⁵-10⁷ K and ~40% in the diffuse phase at T<10⁵ K in low-density regions. The X-ray emission from the warm/hot gas may represent a small (~5%-10%) but important contribution to the X-ray background observed by the ROSAT All-Sky Survey at energies around 1 keV. The best prospects for detection of the warm/hot intergalactic medium of the LSC located in filaments and in the vicinity of virialized regions of groups and clusters are through absorption in resonant lines of O VII and O VIII in soft X-rays and in the O VI doublet in UV. If intergalactic gas in filaments (ρ/<ρ>~1-10) is enriched to typical metallicities of >~0.05, the column densities of O VI, O VII, and O VIII along a random line of sight near the north Galactic pole, especially near the supergalactic plane, have a significant probability to be in the range detectable by current (FUSE, XMM) and future (Constellation-X) instruments.