Zero metallicity stellar sources and the reionization epoch
Abstract
We reconsider the problem of the cosmological reionization due to stellar sources. Using the model developed by Haiman and Loeb (1997), we focus on the effect of changing basic parameters, such as stellar models and spectra, adopted for finding the ionizing photon production rate. In particular we study the zero metallicity limit, which is the natural choice for the first generations of stars. In this case, stellar atmospheres are by far hotter than in the most metal poor cases. From the incomplete and inhomogeneous set of existing models in literature, we construct young isochrones representative of Population III stars and consider the effect of their photon rate emission in the reionization process. The number of ionizing photons emitted by such a zero metal population is about 50% higher than that output by standard metal poor isochrones, all the other parameters of the stellar population and cosmology being unchanged. We find that using suitable zero metallicity models instead of the very metal poor ones, commonly adopted, significantly modifies the reionization epoch.Keywords
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