The escape fraction of ionizing photons during the Epoch of Reionization: observability with the Square Kilometre Array

One of the most important parameters in characterising the Epoch of Reionization, the escape fraction of ionizing photons, fesc, remains unconstrained both observationally and theoretically. With recent work highlighting the impact of galaxy-scale feedback on the instantaneous value of fesc, it is important to develop a model reionization is self-consistently coupled to galaxy evolution. In this work, we present such a model and explore how physically motivated functional forms of fesc affect the evolution of ionized hydrogen within the intergalactic medium. Using the 21cm power spectrum evolution, we investigate the likelihood of observationally distinguishing between a constant fesc and other models that depend upon different forms of galaxy feedback. We find that changing the underlying connection between fesc and galaxy feedback drastically alters the large-scale 21cm power. The upcoming Square Kilometre Array Low Frequency instrument possesses the sensitivity to differentiate between our models at a fixed optical depth, requiring only 200 hours of integration time focused on redshift z = 7.5 − 8.5. Generalizing these results to account for a varying optical depth will require multiple 800 hour observations spanning redshift z = 7 − 10. This presents an exciting opportunity to observationally constrain one of the most elusive parameters during the Epoch of Reionization.