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12.3. Local Dark Baryonic Matter

The baryon density estimated in the Lyalpha at z appeq 3 and in local clusters of galaxies are both similar to the that from SBBN using low D/H. This implies that there is little dark baryonic matter in the universe [190]. This result seems conceptually secure, since there is little opportunity to remove baryons from the IGM at z < 3 or to hide them in dense objects without making stars which we would see [191], and the clusters are believed to be representative of the contents of the universe as a whole today. However, the numerical estimates involved are not yet accurate enough to rule out a significant density (e.g. 0.5 Omegab) of baryonic MACHOS.