Reionization of the universe and the early production of metals

We simulate a plausible cosmological model in considerable physical and numerical detail through the successive phases of reheating (at 10 less than or similar to z less than or similar to 20) and reionization at z approximate to 7. We assume an efficiency of high-mass star formation appropriate to leave the universe, after it becomes transparent, with an ionizing background J(21) approximate to 0.4 (at z = 4), near (and perhaps slightly below) the observed value. Since the same stars produce the ionizing radiation and the first generation of heavy elements, a mean metallicity of [Z/Z(.)] similar to 1/200 is produced in this early phase, but there is a large variation about this mean, with the high density regions having Z/Z(.) approximate to 1/30 and the low density regions (or the Ly alpha forest with N(HI)less than or similar to 10(13.5) cm(2)) having essentially no metals. When it occurs, reionization is very rapid (phase change-like), which will leave a signature that may be detectable by very large area meter-wavelength radio instruments. Also, the background UV radiation held will show a sharp drop of similar to 10(-3) from 1 to 4 ryd because of absorption edges. The simulated volume is too small to form L* galaxies, but the smaller objects that are found in the simulation obey the Faber-Jackson relation. In order to explore theoretically this domain of ''the end of the dark ages'' quantitatively, numerical simulations must have a mass resolution of the order of 10(4.5) M-. in baryons, have high spatial resolution (less than or similar to 1 kpc) to resolve strong clumping, and allow for detailed and accurate treatment of both the radiation field and atomic/molecular physics.