摘要: The baryon density of the universe Ω B is well measured indirectly from Big-Bang nucleo-synthesis, in particular by recent measurements D/H ratio high-redshift QSO absorption systems. In addition, very second maximum power-spectrum CMB fine scale anisotropy allow to constrain at z ≈ 1000. Both results agree and yield = 0.02h −2. Direct diffuse baryonic component (intergalactic gas) redshifts 3 1.5 local are reviewed shown be much more difficult. Available observations consistent with hypothesis that possibly still nearly all baryons located highly ionized Lα forest component, while later epochs contribution a low-density, shock-heated (105–107 K), so called warm-hot intergalactic medium (WHIM), occupies decreasing redshift an increasing fraction baryons. Methods detect this difficulty make quantitative estimates described. 1/3 may hidden WHIM. Yet 1.5, contains least factor 5 less material.
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