A case against baryons in galactic halos

The possibility that galactic halos are composed of baryonic matter is discussed in detail. Specifically, halos composed of snowballs, dust and rocks, planets, s.tars, dead stellar remnants, and hot and cold gas are considered. The serious problems that would arise for each of these types of matter lead us to the conclusion that halos cannot plausibly contain substantial amounts of such matter. This conclusion is considered in relation to big . bangs nucleosynthesis. Various non-baryonic candidates forhalos are also discussed. Submitted to the Astrophysical Journal 2/85. 5 ODerated bv Universities Research Association Inc. under contract with the United States nenartmont nt Fnrrrov