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   PR # 11178
    The discrepancy between the observed baryonic fraction of 20% in clus
    ters and the BigBang nucleosynthesis value of 5% is a major challenge
    to cosmology. In this proposal we will obtain both the baryonic and
    dark matter distributions for 3 high redshift clusters out to a rad-
    ius of 3 Mpc, a factor of 3 larger than done before ASCA.We will thus
    obtain the most precise large scale measurement of the baryonic fract
    ion in clusters.We will also be able to obtain cluster surface bright
    ness profiles out to 5 Mpc and thus search for the predicted "cluster
    edge" where matter is shocked as it flows into the cluster. The exist
    ence of this edge is a general prediction of all theories of cluster
    formation but could not be observed before ASCA.

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