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M. R. Santos, M. Kamionkowski (Caltech)
We analyze the history of dark matter halos with M<109 Msun from the time of CMB-baryon decoupling (z~ 150) to the present (z=0). The extended Press-Schechter merger tree formalism (Lacey & Cole 1993) is used construct realizations of dark matter merger trees. Baryonic cooling models are implemented allowing for atomic and molecular hydrogen cooling, as well as metal cooling via enrichment by Pop III stars. We then calculate the range of allowed stellar contribution of low mass halos to the reionization flux (z~6-10), for given stellar IMF. The current environment of reionization stars and stellar remnants from these halos is studied, with special attention paid to low mass halos which remain isolated through the present epoch, i.e., they have not undergone a major merger since reionization. We model the old stellar populations of these halos, including possible suppression (e.g., Barkana & Loeb 1999) and enhancement (e.g., Cen 2001) of star formation in low mass halos from the reionization radiation, with focus on observational implications.