Summary

• Cosmological simulations: quantitative predictions of the physical properties of the WHIM gas and its observational signatures.

• X-ray emission: mapping 3-D distribution of the WHIM gas. By combining imaging/spectroscopy measurement, X-ray emission shall provide direct evidence of the WHIM gas.

• Cross-correlation with nearby galaxies: X-ray emission lines show strong cross-correlation with nearby large scale structure. Angular correlation: WHIM gas tends to cluster strongly at small angle.

• Future prospective: high spatial/spectral resolution X-ray telescopes.