Can the Photometry of Two z ~ 13 Galaxy Candidates be Explained by a Pop III Starburst?

The discovery of two z ~ 13 galaxy candidates, potentially the farthest objects found in the universe, has the potential of being revolutionary in our understanding of the very early Universe, i.e. the period when the first stars and black holes formed. The two z ~ 13 sources are extremely UV bright, possibly implying either extreme star formation rates or accretion-powered activity by a super-massive black hole of ~10⁸ M_⊙. Here, we study the possibility that the photometry of these sources can be explained by the spectral energy distribution produced by stars born from a top-heavy initial mass function, typical of Pop III stars. We use the code Starburst99 to explore different initial mass functions and different properties of the starburst and identify the region of the parameter space that reproduces the observational properties of the two z ~ 13 sources.